Result
Usually yes, but not in Chicago or MLA. "Through" is a seven-letter preposition, so the guides that capitalize longer prepositions (AP, APA, AMA, and Bluebook) give it a capital. Chicago and MLA lowercase prepositions at any length, so "through" stays lowercase there unless it starts or ends the title.
"Through" by Style Guide
| Style guide | "Through" mid-title | Why |
|---|---|---|
| AP | Capitalize | Prepositions of four or more letters are capitalized |
| APA | Capitalize | Words of four or more letters are capitalized |
| Chicago | Lowercase | Prepositions are lowercase at any length |
| MLA | Lowercase | Prepositions are lowercase at any length |
| AMA | Capitalize | Prepositions longer than three letters are capitalized |
| Bluebook | Capitalize | Prepositions longer than four letters are capitalized |
The Same Headline in Four Styles
| Style | "a walk through the old city" |
|---|---|
| AP | A Walk Through the Old City |
| APA | A Walk Through the Old City |
| Chicago | A Walk through the Old City |
| MLA | A Walk through the Old City |
| Style | "learning through play" |
|---|---|
| AP | Learning Through Play |
| APA | Learning Through Play |
| Chicago | Learning through Play |
| MLA | Learning through Play |
When Chicago Capitalizes "Through"
Chicago lowercases prepositions, but "through" is not always one. When it works as an adverb, it is part of the verb and gets a capital: "How to Follow Through" or "When the Plan Falls Through." The same goes for adjective uses such as "Through Traffic." Ask whether a noun follows the word. If one does ("through the woods"), it is a preposition.
It is also capitalized as the first word ("Through the Looking-Glass") and as the last word in AP, Chicago, and MLA.
Related Words
Other long prepositions split the guides the same way, including "between", "during", "without", and "about". For the full list and the cutoff each guide uses, see title case prepositions.
"Through" in Sentence Case
APA reference lists, many news sites, and most UI text use sentence case instead of title case. There, only the first word and proper nouns get capitals, so "through" is lowercase unless it starts the title: "A walk through the old city." Pick one of the two styles for a whole set of headings rather than mixing them.
Quick Answers
Should "through" be capitalized in a title?
In AP, APA, AMA, and Bluebook, yes. In Chicago and MLA, no, unless it is used as an adverb or sits first or last.
Is "through" capitalized in APA?
Yes. "Through" has seven letters, and APA capitalizes every word of four letters or more.
Is "through" capitalized in Chicago style?
Only as an adverb or adjective ("Follow Through," "Through Traffic") or as the first or last word. As a preposition it stays lowercase.
Is "thru" capitalized the same way?
"Thru" is an informal spelling most style guides avoid in titles. Use "through" and apply the rules above.