Nonverbal behaviors, like smiling, occur during witness testimony in trials. Although it has been acknowledged that witnesses exhibit smiling behaviors, there has been no research examining the subsequent effect of smiling on witness credibility. This study used naturalistic observation to examine smiling behaviors and credibility in actual witnesses testifying in court. Results are examined through quantitative analyses and qualitative descriptions. Raters assessed the smiling behaviors and credibility of 32 male and female witnesses testifying in trials of the Tuscaloosa County Courthouse. "Credibility raters" rated the perceived likeability, trustworthiness, confidence, knowledge, and overall credibility of the witnesses using the Witness Credibility Scale (WCS; Brodsky et al., 2010). "Smile raters" noted smiling frequency and types, including Duchenne (genuine smiles), non-Duchenne (false smiles), speaking/expressive, and listening/receptive smiles. No significant differences were found in the smiling frequency or types for male and female witnesses. All types of smiles besides non-Duchenne were found to contribute to perceived likeability of a witness. Gender was found to affect perceived trustworthiness ratings, in which male witnesses were seen as more trustworthy than female witnesses. Exploratory analyses found significant differences for race, in that African-American witnesses were perceived as less trustworthy, less knowledgeable, and less credible overall than Caucasian witnesses. Other exploratory analyses found that law enforcement witnesses were perceived as more trustworthy, more confidence, more knowledgeable, and more credible overall than other witnesses.