Prior to her election to the House of Representatives, L'Italien worked for Elder Services of Merrimack Valley as a case manager and with the Greater Lawrence Psychological Center working the elder abuse hotline for intakes and referrals.

[4] Representative L'Italien was the author of the landmark legislation on Autism insurance coverage, House Bill 4935 (formerly H. 3809), which requires insurance companies to provide coverage of evidence-based, medically necessary autism therapies, such as applied behavior analysis.

[5] After her House term ended in January 2011, she became director of government affairs for the newly elected Treasurer and Receiver-General of Massachusetts, Steve Grossman until 2012.

[6] L'Italien was elected to the Massachusetts Senate in November 2014 to succeed Barry Finegold in the 2nd Essex and Middlesex seat.

On July 23, 2018, L'Italien appeared on Fox & Friends First and criticized the Trump administration family separation policy.