Nicholas Chong Yen graduated from the University of New Hampshire Franklin Pierce School of Law in 2016, after moving to New Hampshire from Toronto, Canada. Following graduation, he served as an assistant county attorney with the Grafton County Attorney’s Office, where he prosecuted felony cases and worked with the county’s multidisciplinary Sexual Assault Resource Team.

He joined the New Hampshire Attorney General’s Office in 2018 as part of the Drug Prosecution Unit within the Criminal Bureau, focusing on fatal overdose cases. Later that year, he was appointed to lead the Attorney General’s Election Law Unit, where he worked with local and state election officials during several election cycles, including the 2020 primary and general elections. He also prosecuted election law violations, including cases involving voting in more than one state.

Chong Yen returned to the Criminal Bureau in 2019, where he continues to serve as a prosecutor. He works primarily on homicide cases and assists in prosecutions related to alleged sexual abuse at the Youth Development Center. He also oversees all responses to Right-to-Know requests received by the bureau.

In 2025, Attorney General John Formella promoted him to senior assistant attorney general.