Objective: The role of US-detected tenosynovitis (USTS) in the management of rheumatoid arthritis remains controversial. The aim of this study was to investigate whether tenosynovitis can predict a flare in rheumatoid arthritis patients in remission in a real-life cohort. Methods: Rheumatoid arthritis patients from the Swiss Clinical Quality Management cohort were included in this study if they were in clinical remission, defined by 28-joint disease activity score (DAS28-ESR) <2.6, and had an available B-mode tenosynovitis score. The patients were stratified according to the presence or absence of tenosynovitis (USTS+ vs. USTS–). Cox proportional hazard models were used for time-to-event analysis until the loss of remission, after adjustment for multiple confounders. The impact of baseline US performed early in remission and the advent of flares at different fixed time periods after baseline were investigated in sensitivity analysis. Results: Tenosynovitis was detected in 10% of 402 rheumatoid arthritis patients in remission. At baseline, USTS+ patients in remission had significantly higher DAS28-ESR (mean (SD): USTS– 1.8 (0.5) versus USTS+ 2.0 (0.5); p = 0.0019) and higher additional disease activity parameters, such as physician global assessment, and simplified- and clinical-disease activity index. Joint synovitis detected by B-mode US was associated with tenosynovitis (mean (SD) 7.2 (6.3) in USTS– versus 9.0 (5.4) in USTS+, respectively; p = 0.02). A disease flare was observed in 69% of remission phases, with no differences in the time to loss of remission between USTS+ and USTS– groups. Conclusion: While US-detected tenosynovitis was associated with higher disease activity parameters in rheumatoid arthritis patients in clinical remission, it was not able to predict a flare.