This meta-analysis was designed to evaluate the effects of tranexamic acid (TXA) on platelets in patients undergoing cardiac surgery (CS). Relevant trials were identified by computerized searches of PUBMED, Cochrane Library, EMBASE, OVID, China National Knowledge Infrastructure (CNKI), Wanfang Data and VIP Data till Jun 4th, 2022, were searched using search terms "platelet", "Tranexamic acid", "cardiac surgery", "randomized controlled trial" database search was updated on Jan 1st 2023. Primary outcomes included platelet counts, function and platelet membrane proteins. Secondary outcome included postoperative bleeding. Search yielded 49 eligible trials, which were finally included in the current study. As compared to Control, TXA did not influence post-operative platelet counts in adult patients undergoing on- or off-pump CS, but significantly increased post-operative platelet counts in pediatric patients undergoing on-pump CS [(WMD = 16.72; 95% CI 6.33 to 27.10; P = 0.002)], significantly increased post-operative platelet counts in adults valvular surgery [(WMD = 14.24; 95% CI 1.36 to 27.12; P = 0.03). Additionally, TXA improved ADP-stimulated platelet aggression [(WMD = 1.88; 95% CI 0.93 to 2.83; P = 0.0001)] and improved CD63 expression on platelets [(WMD = 0.72; 95% CI 0.29 to 1.15; P = 0.001)]. The current study demonstrated that TXA administration did not affect post-operative platelet counts in adult patients undergoing either on- or off-pump CABG, but significantly increased post-operative platelet counts in pediatric patients undergoing on-pump CS and adults valvular surgery. Furthermore, TXA improved ADP-stimulated platelet aggression and improved CD63 expression on platelets. To further confirm this, more well designed and adequately powered randomized trials are needed.