Computer assisted surgery (CAS) has gained popularity in orthopaedics for both total knee (TKA) and total hip arthroplasty (THA) in the past decades as a stereotactic device that provides the surgeon with real-time feedback on implant position based on electromagnetic or infrared based instruments. The purpose of this study was to assess the effect of CAS on 30-day complication rates following THA and TKA. The American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database was used to identify all patients that underwent THA and TKA from 2011 to 2013, as well as any complication they had within 30-days of their surgery. Univariate and multivariate regression analysis was used to compare the post-operative complications in patients whose surgery involved the use of CAS with those by conventional surgical techniques. We identified 104,550 patients who had THA (42,275 patients) and TKA (62,275 patients) procedures in the database between 2011 and 2013. Computer Assisted Surgery was used in 1,120 THA and 2,173 TKA procedures. There were higher overall adverse events (OR 1.40, CI: 1.22–1.59) in the Conventional group when compared to CAS for TKA. The rate of overall minor events (OR 1.38, CI: 1.21–1.58) and requirements for blood transfusion (OR 1.44, CI: 1.25–1.67) were higher in the Conventional group compared to the CAS group for TKA. However, rate of re-operation was significantly higher in the CAS group for TKA (OR 1.60, CI: 1.15–2.25). The results also showed higher overall adverse events (OR 2.61, CI: 2.09–3.26) in the Conventional group when compared to CAS for THA. The rate of overall minor events (OR 2.72, CI: 2.16–3.42) and requirements for blood transfusion (OR 3.27, CI: 2.52–4.25) was higher in the Conventional group whereas superficial wound infections (OR 0.46, CI: 0.46–0.81) were shown to be higher in the CAS group. The result also showed slightly longer operative times in CAS for both THA and TKA. This study analysed a large patient database involving multiple institutions and surgeons and found that, overall, the use off CAS in primary total hip and total knee arthroplasty reduced the number of adverse events in the first 30-days postoperatively, compared to conventional surgical techniques. However, CAS was associated with an increased number of reoperations, superficial infections and operating time. The clinical benefits and disadvantages of CAS should be considered by arthroplasty surgeons when determining the potential benefit-cost ratio of this technology.