Background Social media is an effective channel for the advancement of women physicians; however, its use by women in cardiology has not been systematically studied. Our study seeks to characterize the current Women in Cardiology Twitter network. Methods and Results Six women-specific cardiology Twitter hashtags were analyzed: #ACCWIC (American College of Cardiology Women in Cardiology), #AHAWIC (American Heart Association Women in Cardiology), #ilooklikeacardiologist, #SCAIWIN (Society for Cardiovascular Angiography and Interventions Women in Innovations), #WomeninCardiology, and #WomeninEP (Women in Electrophysiology). Twitter data from 2016 to 2019 were obtained from Symplur Signals. Quantitative and descriptive content analyses were performed. The Women in Cardiology Twitter network generated 48 236 tweets, 266 180 903 impressions, and 12 485 users. Tweets increased by 706% (from 2083 to 16 780), impressions by 207% (from 26 755 476 to 82 080 472), and users by 440% (from 796 to 4300), including a 471% user increase internationally. The network generated 6530 (13%) original tweets and 43 103 (86%) amplification tweets. Most original and amplification tweets were authored by women (81% and 62%, respectively) and women physicians (76% and 52%, respectively), with an increase in original and amplification tweets authored by academic women physicians (98% and 109%, respectively) and trainees (390% and 249%, respectively) over time. Community building, professional development, and gender advocacy were the most common tweet contents over the study period. Community building was the most common tweet category for #ACCWIC, #AHAWIC, #ilooklikeacardiologist, #SCAIWIN, and #WomeninCardiology, whereas professional development was most common for #WomeninEP. Conclusions The Women in Cardiology Twitter network has grown immensely from 2016 to 2019, with women physicians as the driving contributors. This network has become an important channel for community building, professional development, and gender advocacy discussions in an effort to advance women in cardiology.