In experiment 1, 267 undergraduates read a case summary and witness statement. Sex and age of the witness (49, 69, 79 or 89 years) were varied. Participants rated the witness's perceived convincingness, confidence, quality of observation, accuracy, honesty, competence, memory, suggestibility, and cognitive functioning. As well as an age effect for honesty, age by sex interactions were observed for several characteristics, particularly for comparisons of the 79-year-olds versus the 49-year-olds, and 89-year-olds versus the 49-year-olds. In experiment 2, 94 undergraduates read the same testimony given by a 79-year-old male or female witness, and completed the Fraboni Scale of Ageism and the Aging Semantic Differential. Participants who evidenced stronger aging stereotypes on these measures rated the witness less favorably than did participants who were less prejudiced. This experiment is the first to show a link between perceived credibility of older adults and ageist attitudes. Practical applications regarding how older witnesses are viewed by jurors, and the criminal justice system more generally, are discussed.