Social cues are used to facilitate online science communication, yet little is known about how they may play a role in online public engagement with science sites. This mixed-method study investigates r/science Ask Me Anything (AMA) sessions on Reddit through content analysis and an online survey to identify the types and variations of social cues manifested in six r/science AMAs across varying disciplines. The study's contributions are twofold. One is to investigate social cue uses in online science communication; the other is to develop a coding scheme for social cues that incorporates both positive and negative social cues in the analysis.