Introduction The guidelines recommend a beta-blocker or calcium channel blocker as the first-line medication for angina, supplemented by other agents for additional symptoms. One such agent is trimetazidine (TMZ), which has been shown to reduce the frequency of anginal episodes and improve exercise performance without affecting haemodynamic parameters. However, extensive real-world evidence for its efficacy in combination with first-line therapies has been lacking. Methods The aim of this large-scale, Russian, multicentre, 6-month, open-label, prospective observational study was to assess the effect of adding TMZ modified release 35 mg bid to background antianginal therapy in the real-world clinical setting. Results The study included 896 patients: 54% women, aged 29–90 years (42.6% >65 years), 63% with class II angina, and receiving beta-blockers alone or in combination (93%). Add-on TMZ reduced angina frequency and short-acting nitrate use within 2 weeks (both p < 0.0001) regardless of background therapy and maintained this effect over 6 months. It increased the proportion of patients with class I angina sixfold while decreasing that of class 3 angina almost fourfold. It also improved walking distance and well-being at 6 months (both p < 0.0001). Treatment was well tolerated. Conclusion Add-on TMZ is a safe and rapidly effective treatment for reducing angina attacks and nitrate use in the real-world clinical setting. It also increases exercise capacity and well-being. These effects are observed within 2 weeks and persist for at least 6 months.