As part of a program evaluation of the New York City Test & Trace program (T2)—one of the largest such programs in the USA—we conducted a study to assess how implementing organizations (NYC Health + Hospitals, government agencies, CBOs) communicated information about the T2 program on Twitter. Study aims were as follows: (1) quantify user engagement of posts (“tweets”) about T2 by NYC organizations on Twitter and (2) examine the emotional tone of social media users’ T2-related tweets in our sample of 1987 T2-related tweets. Celebrities and CBOs generated more user engagement (0.26% and 0.07%, respectively) compared to government agencies (e.g., Mayor’s Office, 0.0019%), reinforcing the value of collaborating with celebrities and CBOs in social media public health campaigns. Sentiment analysis revealed that positive tweets (46.5%) had higher user engagement than negative tweets (number of likes: R2 = .095, p < .01), underscoring the importance of positively framing messages for effective public health campaigns.