Background: The protective effect of a healthy diet combined with stair climbing on cardiovascular health is unclear. We aimed to assess the independent and joint associations of dietary patterns and stair climbing with major adverse cardiovascular events (MACEs). Methods: We included 117,384 participants with information on dietary intake and stair climbing from the UK Biobank (UKBB). We excluded participants with MACEs at baseline and death within two years of follow-up. We used restricted cubic spline (RCS) plots describing the linear or nonlinear associations between dietary patterns (the alternate Mediterranean diet score (AMED), dietary approaches to stop hypertension (DASH), the healthful planted-based diet index (HPDI) and the alternate healthy eating index-2010 (AHEI-2010)) and stair climbing and MACEs. COX regressions estimated the hazard ratios (HRs) for incident MACEs associated with dietary patterns combined with stair climbing, and adjusted for sociodemographic, lifestyle and medical factors. Results: The UKBB documented 9408 MACEs over a median follow-up of 13.3 years. Four dietary patterns were negatively and linearly associated with MACEs (P-nonlinear > 0.05), whereas daily stair climbing was negatively and nonlinearly associated with MACEs (P-nonlinear = 0.011). All of the dietary patterns had significant multiplicative interactions with stair climbing (all p-values < 0.05). The three dietary patterns had the lowest risk ratios for MACEs in the highest tertile (T3) combined with daily stair climbing of 60–100 steps (AMED: 0.78 (0.68, 0.89), DASH: 0.80 (0.70, 0.91) and HPDI: 0.86 (0.75, 0.98)), whereas the AHEI-2010 had the lowest HRs for MACEs in the T1 combined with stair climbing of 110–150 steps (AHEI-2010: 0.81 (0.71, 0.93)). Conclusions: Maintaining healthy dietary patterns and adhering to an average of 60–100 steps of stair climbing per day at home can be effective in preventing cardiovascular health-related events.