To investigate the characteristics of olaparib-associated adverse events (AEs) in cancer patients. Databases were searched for phase II and III randomized controlled trials (RCTs) involving olaparib treatment up to March 2024. A systematic assessment was performed. Twenty-seven RCTs involving 9542 patients were included. This meta-analysis indicates that olaparib could significantly increase the risk of developing any all-grade (RR, 1.08; 95% CI, 1.03-1.13; p = 0.001) and high-grade (RR, 1.45; 95% CI, 1.19-1.77; p = 0.0003) AEs in cancer patients. Olaparib could increase the risk of dose reduction (RR, 3.00; 95% CI, 1.59-5.70; p = 0.0007) and treatment discontinuation (RR, 2.00; 95% CI, 1.28-3.14; p = 0.002). Hematologic toxicities and gastrointestinal toxicities commonly occur in patients receiving olaparib. Anemia, nausea, and fatigue were the most frequent AEs, with olaparib increasing the risk of both all-grade and high-grade occurrences of these events. Patients with longer treatment durations tend to have a higher risk of anemia. Patients with urinary system tumors tend to have a higher risk of nausea, while those with breast cancer tend to have a higher risk of fatigue. Olaparib maintenance therapy may be associated with a higher risk of fatigue. Olaparib could increase other AEs such as diarrhea, vomiting, decreased appetite, dyspepsia, dysgeusia, dizziness, headache, back pain, urinary tract infection, dyspnea, and cough. Olaparib-containing therapy could increase the occurrence of specific AEs in patients with cancer. Clinicians should be aware of these risks and conduct regular monitoring.