The changes in cardiac function that occur after pericardiocentesis are unclear. An understanding of the effect of pericardiocentesis on right ventricular (RV) and left ventricular (LV) function is clinically important. This study was performed to assess RV and LV function with echocardiography before and after pericardiocentesis. In total, 19 consecutive patients who underwent pericardiocentesis for more than moderate pericardial effusion were prospectively enrolled from August 2015 to October 2017. Comprehensive transthoracic echocardiography was performed before, immediately after (within 3 h), and 1 day after pericardiocentesis to investigate the changes in RV and LV function. The mean age of all patients was 72.6 ± 12.2 years. No pericardiocentesis-related complications occurred during the procedure, but one patient died of right heart failure 8 h after pericardiocentesis. After pericardiocentesis, RV inflow and outflow diameters increased (p < 0.05 versus values before pericardiocentesis), and the parameters of RV function (tricuspid annular plane systolic excursion, tricuspid lateral annular systolic velocity, fractional area change, and RV free wall longitudinal strain) significantly decreased (p < 0.001 versus values before pericardiocentesis). These abnormal values or RV dysfunction remained 1 day after pericardiocentesis (p > 0.05 versus values immediately after pericardiocentesis). Conversely, no parameters of LV function changed after pericardiocentesis. Of 19 patients, 13 patients showed RV dysfunction immediately after pericardiocentesis and 6 patients did not. RV free wall longitudinal strain before pericardiocentesis in patients with post-procedural RV dysfunction was reduced compared to those without post-procedural RV dysfunction ( − 18.9 ± 3.6 versus − 28.4 ± 6.3%; p = 0.005). The area under the curve values for prediction of post-procedural RV dysfunction was 0.910 for RV free wall longitudinal strain. The occurrence of RV dysfunction after pericardiocentesis should be given more attention, and pre-procedural RV free wall longitudinal strain may be a predictor of post-procedural RV dysfunction.