Background: Longitudinal association of television (TV) viewing and moderate- to vigorous-intensity physical activity (MVPA) with pericardial adipose tissue (PAT) is unclear. Methods: We studied Coronary Artery Risk Development in Young Adults Study participants transitioning from early to middle age at Coronary Artery Risk Development in Young Adults (CARDIA) exam years 15 (2000–2001; N = 1975, mean age = 40.4, 55.4% women, 45.3% Black) and 25 (2010–2011). TV viewing (in hours per day) and MVPA (in exercise units) were measured using a self-report questionnaire. PAT volume (in milliliters) was measured using computed tomography. Multivariable linear regression was used to examine the associations of tertiles of 10-year change (years 25–15) in TV viewing and MVPA with a concurrent change in PAT with adjustments for covariates. Results: Participants in the highest tertile of 10-year increase in TV viewing had a greater increase in PAT (β = 2.96 mL, P < .01). Participants in both middle (β = −3.93 mL, P < .01) and highest (β = −6.22 mL, P < .01) tertiles of 10-year changes in MVPA had smaller mean increases in PAT over 10 years when compared with the lowest tertile in fully adjusted models. Conclusions: Reducing or maintaining early-midlife levels of TV viewing and increasing MVPA may be associated with less PAT accumulation with age.