Despite growing recognition of the importance of sex and gender considerations in health research, they are rarely integrated into research design and reporting. The authors sought to assess the integration of sex, as a biological attribute, and gender, as a socially constructed identity, in published reporting guidelines. They conducted a systematic review of published reporting guidelines listed on the EQUATOR website from inception until December 2018. They selected all reporting guidelines (original and extensions) listed in the EQUATOR library. A total of 407 reporting guidelines were included; they were published between 1995 and 2018. Of the 407 guidelines, 235 (57.7%) mentioned at least one of the sex- and gender-related words. In the checklist of the reporting guidelines (n = 363), “sex” and “gender” were mentioned in 50 (13.8%) and 40 (11%), respectively. Only one reporting guideline met our criteria (nonbinary, appropriate categorization, and non-interchangeability) for correct use of sex and gender concepts. They assessed the integration of sex and gender in reporting guidelines based on the use of sex- and gender-related words. Their findings showed a low use and integration of sex and gender concepts and their incorrect use. Authors of reporting guidelines should reduce this gap for a better use of research knowledge.