Thematic ETFs vs. Sector ETFs: What Is the Difference?

By Adam Patti, Chief Executive Officer, VistaShares | Published November 13, 2026

Sector ETFs hold companies grouped by a standard industry classification, such as all energy or all health care companies, so their boundaries are fixed and widely shared. Thematic ETFs hold companies tied to a trend, such as artificial intelligence, electrification or space, which usually cuts across several sectors. Sector funds slice the market by what companies are today; thematic funds group them by where spending and demand may be heading.

What is a sector ETF?

A sector ETF invests in companies from one part of the economy as defined by an industry classification system. The most widely used is the Global Industry Classification Standard, developed by MSCI and S&P Dow Jones Indices, which organizes companies into four levels: 11 sectors, 25 industry groups, 74 industries and 163 sub-industries, according to MSCI’s April 2026 methodology.¹ Each company is assigned to one sub-industry based on its principal business activity.

Because classifications are standard and public, sector ETFs from different sponsors covering the same sector tend to hold similar companies. Sector funds are common tools for adjusting a portfolio’s exposure, for example adding to health care or reducing technology.

What is a thematic ETF?

A thematic ETF invests in companies linked to a specific trend or structural change, regardless of which sector they belong to. An AI infrastructure fund might hold semiconductor designers (information technology), electrical equipment makers (industrials), utilities (utilities) and data center operators (real estate). An electrification fund might combine miners, cable makers, grid equipment companies and power producers.

There is no standard definition of any theme, so each sponsor draws its own boundaries. Two funds with similar names can hold very different companies. Our article on how to evaluate a thematic ETF offers a checklist.

How do they compare?

Definition: sector funds follow a standard, shared classification. Thematic funds follow each sponsor’s definition of the theme.

Breadth: a sector fund stays within one sector. A thematic fund usually spans several sectors.

Comparability: sector funds covering the same sector are usually similar. Thematic funds with similar names can differ widely.

Holdings stability: sector membership changes only when a company’s business changes or the classification is revised. Thematic holdings can change as the theme evolves and as sponsors refine their rules.

Concentration: both can be concentrated. Large sectors, such as information technology, can be dominated by a few companies; thematic funds may hold a small number of names or many small companies.

Cost: broad sector index funds are often among the lower-cost ETFs. Thematic funds, especially actively managed or research-intensive ones, typically charge more.

Why would an investor choose a thematic fund over sector funds?

A theme rarely fits inside one sector. The buildout of AI data centers draws on chips, servers, power equipment, cooling, construction and electricity. An investor trying to capture that buildout with sector funds would need several of them and would end up owning many companies with little connection to the theme. A thematic fund assembles the relevant companies across sectors in one portfolio.

Thematic funds can also be built around how a trend is funded. Approaches such as bill of materials investing map where a buildout’s spending goes and allocate accordingly, an option that sector classification does not provide. Our article on what a supercycle is in investing describes the kind of multiyear spending cycles thematic funds often target.

Why would an investor choose sector funds instead?

Clarity: standard definitions make it easy to know what is owned and to compare funds.

Cost: broad sector funds are often inexpensive.

Liquidity: many sector ETFs trade heavily, with narrow spreads.

Portfolio control: sector funds let investors adjust exposure to parts of the economy precisely, without the overlap that themes can create.

Durability: sectors persist; themes can fade, and some thematic funds have closed when interest waned. Our article on what happens when an ETF closes explains the process.

What are the main risks of each?

Sector ETFs: exposure to a single part of the economy, sensitivity to the sector’s cycle, such as commodity prices for energy or interest rates for financials and utilities, and concentration in the sector’s largest companies.

Thematic ETFs: dependence on the theme playing out as expected, valuation risk when a theme is popular, inconsistent definitions, higher costs, possible concentration in smaller or more volatile companies and the risk that the fund closes if assets remain small. Our article on ETF concentration risk discusses concentration in both types.

How do they fit together in a portfolio?

A common structure keeps a diversified core, such as a broad index fund, and adds smaller satellite positions. Sector funds can tilt the core toward or away from parts of the economy. Thematic funds can add exposure to specific long-term trends. Because broad index funds already include every sector, both kinds of satellite overlap partly with the core. Checking overlap helps avoid owning more of the largest companies than intended.

How can investors tell what a fund really holds?

Read the prospectus or index methodology: for thematic funds, look at how companies qualify for the theme, for example revenue thresholds or supply chain roles.

Check the sector breakdown: a thematic fund’s sponsor usually publishes its exposure by sector, which shows how many parts of the economy it spans.

Review the top holdings and their weights: these show concentration and overlap.

Look at daily holdings: most ETFs publish their full portfolio each business day.

More ETF comparisons are in the ETF Basics Guide, and the Thematic ETF Guide covers themes in depth.

Frequently asked questions

Is a technology ETF a sector ETF or a thematic ETF?

A fund that holds companies classified in the information technology sector is a sector ETF. A fund built around a technology trend, such as AI or cybersecurity, that draws companies from several sectors is a thematic ETF. The name alone does not settle it; the selection rules do.

How many sectors are there?

Under the Global Industry Classification Standard, there are 11 sectors, divided into 25 industry groups, 74 industries and 163 sub-industries, according to MSCI’s April 2026 methodology. The structure is reviewed periodically, and changes can move companies between sectors.

Are thematic ETFs riskier than sector ETFs?

Often, though not always. Thematic funds depend on a specific trend, can be concentrated in smaller or more volatile companies and may close if they fail to gather assets. Some sector funds are also highly concentrated or cyclical. Risk depends on each fund’s holdings and weights.

Why do two thematic ETFs with similar names hold different stocks?

There is no standard definition of a theme. Each sponsor decides which activities count, how much revenue a company must earn from the theme and how to weight holdings. As a result, two AI or clean energy funds can have very different portfolios.

Can a thematic ETF replace sector funds?

Not usually. A thematic fund spans parts of several sectors and leaves out companies unrelated to the theme. Sector funds give precise exposure to each part of the economy. Investors typically use them for different purposes.

Do sector and thematic ETFs overlap with broad index funds?

Yes, often substantially. Broad index funds such as those tracking the S&P 500 include companies from every sector, and many large thematic holdings are also large index holdings. Measuring overlap shows how much distinct exposure a sector or thematic fund adds.

Cite this page: Adam Patti, "Thematic ETFs vs. Sector ETFs: What Is the Difference?," VistaShares, updated November 13, 2026, https://www.vistashares.com/thematic-vs-sector-etfs/. Plain-text version.

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