Breast cancer is the most common malignancy in women worldwide. Even minor breast surgery can cause significant postoperative pain (PP). PP can turn into chronic pain in 25-40% of cases. Inadequate PP control is associated with increased morbidity, delayed wound healing, prolonged hospital stay, increased opioid use and side effects, and high cost of care. Opioid use remains the mainstay of postoperative analgesia. Opioids, especially morphine, inhibit both cellular and humoral immune functions. This effect may be responsible for the high rates of local recurrence and/or metastasis after surgery. Additionally, studies have shown that perioperative opioid use is associated with social abuse. This demonstrates the importance of reducing perioperative opioid use. Currently, multimodal analgesia based on nerve block is being widely investigated and has shown encouraging clinical results. Numerous regional analgesic techniques have been investigated in breast cancer surgery, including intercostal nerve block, thoracic epidural anesthesia, and paravertebral block. Compared with general anesthesia alone, it reduces the postoperative pain score even after a single-shot injection for up to 72 hours, reduces opioid consumption, improves the quality of patient recovery, and suppresses the development or reduces the severity of chronic pain. Serratus anterior plane block (SAPB) is reported to be effective in perioperative pain management of breast cancer surgeries. The important problem of SAPB block is that it is insufficient to block the anterior cutaneous branches of the intercostal nerves. Therefore, intravenous analgesia is required. Thoracic transversus muscle plane block (TTPB) is a recently described fascial plane block used to anesthetize the anterior cutaneous branches of the intercostal nerves from T2-T6. Its effectiveness has been demonstrated for breast surgery and median sternotomy. In our study, we will provide postoperative analgesia in patients undergoing breast surgery by applying the serratus anterior block in combination with the transversus thoracis plane block. Since we avoid complicated analgesia methods such as paravertebral block, the risk of complications will be reduced. In this study, we aimed to compare the effectiveness of the combination of SAPB and TTPB with SAPB performed alone in breast cancer surgery.