After studying at Hunter College and the Boston Conservatory of Music, Simard moved to New York, where she appeared in Forbidden Broadway '93. She made her Broadway debut in The 25th Annual Putnam County Spelling Bee and later performed in the Broadway productions of Shrek The Musical and Sister Act. Simard received Drama Desk Award nominations for Outstanding Featured Actress in a Musical for her roles in I Love You, You're Perfect, Now Change, The Thing About Men, and . Simard originated the role of Sister Mary Downy in the 2016 Broadway musicalDisaster!, for which her performance earned her a Tony Award nomination and a Drama League Award nomination in 2016. She was also nominated for a Drama Desk Award for the same role, which she performed off Broadway in 2014. The Variety reviewer wrote: "...this is a good cast that knows the comic ropes — and then some, in the special case of Jennifer Simard, who shows great comic chops as a nun with a secret gambling fixation.“ She appeared on Broadway as Ernestina in the 2017 revival of Hello, Dolly!, starring Bette Midler and David Hyde Pierce. Simard played Miss Hannigan in the St. Louis Muny production of Annie from July 18–25, 2018. The reviewer wrote: "Jennifer Simard...plays Miss Hannigan, and is nothing less than incredible in the role. She is hilarious as the head of the orphanage, causing the crowd to burst into laughter for much of her time on-stage. Her rendition of “Little Girls” is not to be missed. With impeccable comedic timing, a wonderful voice, and all-around talent – Simard gives a performance that makes it impossible to look away." In August 2018, it was announced that Simard would be joining the company of the Tony-nominated musical Mean Girls as Mrs. Heron, Ms. Norbury, and Mrs. George in September 2018, replacing Kerry Butler. Her last performance was on December 8, 2019. In October 2019, it was announced that Simard would be joining the company of the gender-swapped revival of Company as Sarah.
On October 3, 2004, she married Brad Robertson, whom she met when he was the light board operator for the off-Broadway production of I Love You, You're Perfect, Now Change.
