A vowel sound that glides from one position to another in a single syllable, like the sound in coin. Kids do not need the term; they need the two spellings and where each one stands.

How is this like ai and ay?

Same bargain: the i-spelling usually works inside words, the y-spelling usually takes the ends. Kids who learned ai/ay usually adopt oi/oy in one sitting.

1st grade diphthongs oi and oy

1st grade diphthongs oi and oy worksheets

Oi and oy spell the gliding vowel sound in coin and boy. First graders sort by position and absorb the pattern: oi usually inside the word, oy usually at the end.

Free printable PDF worksheet, aligned to Common Core RF.1.3.c.

Each print is a different sheet with its own answer key. You don't need to sign up.

The kind of words you'll complete and sort

Fill in the missing letters to make a real word, then write the whole word in its column.

jntblahfljster (a shellfish that can hold a pearl)

Columns: oi and oy. Only oi turns "b_l" into a real word, so boil goes under oi; the clue (a shellfish that can hold a pearl) picks oy for "_ster", so oyster goes under oy.

Every print pulls a new set of words at this level, so a make-up test or a second sibling gets a different mix.

What's on a 1st grade sheet

1st grade sheets draw from 26 words, 10 to a page. All 26 are on 2nd grade sheets too, along with 1 more. 2nd grade sheets print 14 to a page.

Some of the words:

coinoilsoiljoinvoicenoisefoiltoyroyalvoyage

Complete and sort. Fill in the missing letters to make a real word, then write the whole word in its column. 10 words per page.

Every version prints on US Letter or A4, with its answer key on the last page.

How to teach this

Before sorting, have your child underline where the sound lives in each word: middle or end. The position, not the sound, makes the choice here, and underlining shifts their eyes to it.

Watch for: This is a position pattern, the same shape as ai/ay: oi inside before a consonant (boil, point), oy at the end (toy, enjoy) or before a vowel (royal, voyage). English words essentially never end in oi. A few words break the pattern, like oyster, and are learned by sight. A diphthong is a vowel sound that glides: the mouth moves while saying it. Have your child watch their lips in a mirror on 'oil' and feel the slide.

Common questions about 1st grade diphthongs oi and oy

What is a diphthong?: A vowel sound that glides from one position to another in a single syllable, like the sound in coin. Kids do not need the term; they need the two spellings and where each one stands.
How is this like ai and ay?: Same bargain: the i-spelling usually works inside words, the y-spelling usually takes the ends. Kids who learned ai/ay usually adopt oi/oy in one sitting.

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Aligned to Common Core RF.1.3.c. Reviewed by the One more sheet team. Content version 241, updated October 2026.

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