Recent work suggests that inadequate sleep increases economic burden and reduces workplace productivity, and sleep patterns are becoming more variable within Western societies. Few studies have examined the relationship between intraindividual variability (IIV) in sleep patterns and cognition, despite the potential importance of this relationship for daytime function. Studies examining this relationship have considered a narrow range of cognitive functions, and have methodological limitations, such as failure to adjust for sleep duration in analyses, and the use of techniques that falter when data distributions are non-normal. The current study examined the relationship between actigraphically-assessed sleep IIV and neuropsychological test performance using statistical methodology that accounts for these limitations. It was hypothesized that greater IIV in sleep duration and timing would be associated with poorer neuropsychological test performance, independent of average sleep patterns. One hundred thirty-three young adults underwent seven days of actigraphic sleep assessment, followed by a battery of neuropsychological tests targeting attention, learning and memory, and executive function. Robust multiple regressions and negative binomial regressions in a Bayesian framework were used to assess the relationship between sleep IIV and test performance, adjusting for average sleep patterns. Results revealed practically null relationships between mean sleep duration and verbal recognition, as well as mean sleep timing and false positives in a verbal recognition task. While a marginally non-zero association between sleep timing IIV and attention was observed, this association fell short of acceptable credibility. No other credible relationships were found. Results of the current study did not support a relationship between sleep IIV and cognition. Future studies may benefit from longer sleep pattern assessments, the use of upcoming purpose-built statistical methods for assessing IIV with few repeated measures, and consideration of biological and environmental confounds of this potential relationship.