She is a graduate of Manchester High School (1960), the University of Connecticut (1964)[1], and the Harvard Graduate School of Education (1965)[2].

She was a high school English teacher in Arlington, MA (1965—66) and the assistant director of Harvard's Project Upward Bound (1967). In New York City, she worked on early childhood research projects for General Learning Corp. (1967—69) and was the Director of Publications for the National Commission on Resources for Youth (1970—71). For 20 years from 1972—1992, Jean Marzollo was editor of Scholastic's "Let's Find Out" Magazine [3], working closely with art director Carol Devine Carson. She has written books for teachers and parents, as well as articles about children for Parents Magazine [4], Redbook, and other parenting magazines.

Jean Marzollo is best known for her award-winning, best-selling (The New York Times Best Seller List) I SPY series with photographic illustrator Walter Wick. Among her other children's books are: Mama Mama and Papa Papa; Close Your Eyes; Pretend You're a Cat; Happy Birthday, Martin Luther King; and the Shanna Show books. After more than twenty years of writing children's books, she began to illustrate them, too. She has retold and illustrated five Bible stories and three Greek myths, as well as writing and illustrating two counting books for preschoolers: Ten Little Eggs and Ten Little Christmas Presents.

In recent years she has developed online, interactive books for young children to play on computers and on interactive whiteboards, such as SMART Boards.

She is married to Claudio Marzollo, a retired sculptor who has co-authored some of her children's science fiction and fantasy books. They have two sons, Dan Marzollo (b. 1973) and Dave Marzollo (b. 1975), who ghostwrite many of the I SPY Challengers and the I SPY readers under Jean's supervision, and who have co-authored some of her sports books for kids. She resides in Upstate New York.

9 Months 1 Day 1 Year: A Guide to Pregnancy, Birth and Babycare,39 Kids on the Block: Chicken Pox Strikes Again #5,39 Kids on the Block: My Sister the Blabbermouth #6,39 Kids on the Block: Roses are Pink and You Stink #3,39 Kids on the Block: The Best Friends Club #4,39 Kids on the Block: The Best Present Ever #2,39 Kids on the Block: The Green Ghost of Appleville #1,Amy Goes Fishing,Baby Unicorn and Baby Dragon,Baby's Alphabet,Baseball Brothers,Basketball Buddies,Baxter Bear’s Bad Day,Birthday Parties for Children,Blue Sun Ben,Cannonball Chris,Christmas Cats,Cinderella,City Sounds,Close Your Eyes,Daniel in the Lions' Den,David and Goliath,Do You Know New?,Do You Love Me, Harvey Burns?,Doll House Adventure,Doll House Christmas,Fathers & Babies,Fathers & Toddlers,Football Friends,Getting Your Period,Halfway Down Paddy Lane,Halloween Cats,Happy Birthday, Martin Luther King,Helping Hands Handbook,Hockey Hero,Home Sweet Home,How Kids Grow,I Am a Leaf,I Am a Rock,I Am a Star,I Am an Apple,I Am Fire,I Am Planet Earth,I Am Snow,I Am Water,I Love You: A Rebus Poem,I See a Star: A Christmas Rebus Story,I Spy A Balloon,I Spy A Butterfly,I Spy A Candy Cane,I Spy a Dinosaur's Eye,I Spy a Penguin,I Spy A Pumpkin,I Spy A Scary Monster,I Spy A School Bus,I Spy A Skeleton,I Spy A to Z,I Spy Christmas,I Spy Extreme Challenger,I Spy Fantasy,I Spy Fun House,I Spy Funny Teeth,I Spy Gold Challenger,I Spy I Love You,I Spy Lightning in the Sky,I Spy Little Animals,I Spy Little Book,I Spy Little Bunnies,I Spy Little Christmas,I Spy Little Hearts,I Spy Little Letters,I Spy Little Numbers,I Spy Merry Christmas,I Spy Little Wheels,I Spy Mystery,I Spy Phonics Fun,I Spy Santa Claus,I Spy School Days,I Spy Spooky Night,I Spy Super Challenger,I Spy Treasure Hunt,I Spy Ultimate Challenger!,I Spy Year-Round Challenger!,I Spy: A Book of Picture Riddles,I’m A Seed,I’m Tyrannosaurus!,I'm a Caterpillar,In 1492,In 1776,Jed and the Space Bandits,Jed’s Junior Space Patrol,Jonah and the Whale (and the Worm),Learning through Play,Let's Go, Pegasus!,Little Bear, You're A Star!,Mama Mama,Miriam and Her Brother Moses,My First Book of Biographies,Once Upon a Springtime,Pandora's Box,Papa Bear’s Party,Papa Papa,Pierre the Penguin,Pizza Pie Slugger,Pretend You’re a Cat,Red Ribbon Rosie,Red Sun Girl,Robin of Bray,Ruth and Naomi,Ruthie’s Rude Friends,Shanna's Animal Riddles,Shanna's Ballerina Show,Shanna's Bear Hunt,Shanna's Doctor Show,Shanna's Hip, Hop, Hooray!,Shanna's Lost Shoe,Shanna's Party Surprise,Shanna's Pizza Parlor,Shanna's Princess Show,Shanna's Teacher Show,Slam Dunk Saturday,Snow Angel,Soccer Cousins,Soccer Sam,Sun Song,Superkids,Supertot,Ten Cats Have Hats,Ten Little Christmas Presents,Ten Little Eggs,Thanksgiving Cats,The Baby Unicorn,The New Kindergarten,The Rebus Treasury,The Silver Bear,The Teddy Bear Book,Think! Draw! Write!,Three Little Kittens,Uproar on Holler Cat Hill,Valentine Cats,Your Maternity Leave: How to Leave Work, Have a Baby, and Go Back to Work Without Getting Lost, Trapped, or Sandbagged Along the Way