<p>This systematic review aimed to identify how recent scientific literature has conceptualized and measured family acceptance and rejection of sexual minority youth and young adults. We conducted a search in the Web of Science (WoS) and SCOPUS databases from 2017 to 2022. We identified 33 studies which included measures of family acceptance, rejection, and support focused on sexual orientation. Our results showed differences in the operationalization of these attitudes—including whether they are conceptualized as a negative-positive continuum, as family dynamics independent of sexual orientation, or as attitudes that change over time—and in how they are captured by instruments. The most common source of support assessed was family as a whole, followed by parents (either separately or as a couple). The support received from other family members, such as with siblings and other relatives, was less frequently assessed. Our findings indicate that there are diverse ways of operationalizing family attitudes towards the sexual orientation of a young family member, which can provide different information regarding predictors, outcomes, and life trajectories of sexual minority individuals. We suggest the need for researchers to consider that acceptance and rejection attitudes can co-exist in the same family; and to distinguish the assessment of overall family support versus support related to the individual’s sexual orientation. Moreover, our findings suggest examining family acceptance and rejection for diverse sexual orientation and identities, to detect resources and challenges that are specific to monosexual, plurisexual, and asexual individuals within their family contexts.</p>