Introduction Total hip (THA) and knee arthroplasties (TKA) are common elective procedures, and dedicated arthroplasty teams perform multiple procedures per day. Little is documented about how time-of-day scheduling affects the intraoperative efficiency of total joint arthroplasties (TJA). In this study, we analyzed the effects of surgical start time on TJA operative lengths. Methods A retrospective study was performed for primary TJA patients done within a four-year period at a single academic medical center. Surgical start time, operative duration, and patient demographics were collected. Based on a 12-hour operative day, surgical start times were categorized as early (7AM to 11AM), mid-day (11AM to 3PM), or late (after 3PM). A chi-squared test was performed to examine for associations between patient demographics and surgical start time. A multivariate linear regression (MLR) was performed to determine the effect of surgical start time on operative duration. P-values less than 0.05 were considered significant. Results This study identified 1663 TJAs – 869 total knee (TKA) and 791 total hip arthroplasties (THA) who met inclusion criteria. Among TKAs, we identified 319 (36.7%) early, 437 (50.3%) mid-day, and 113 (13.0%) late operations. Among THAs, we identified 407 (51.4%) early, 297 (37.5%) mid-day, and 87 (11.0%) late operations. MLR demonstrated that for TKA there was a 4.9 (p =0.018) and 7.3 (p=0.013) minute increase for mid-day and late cases, respectively. For THAs, a non-early start time was associated with an increased operative duration of 9.1 to 12 minutes (p<0.001). Discussion Surgical start time has a statistically significant, but minimal, effect on operative length for TJAs, with later cases being slightly longer than first-start cases.