Aim: Methotrexate, a structural counterpart of folic acid, is well recognized as a very efficacious pharmaceutical agent utilized in the treatment of several pediatric oncological conditions. A high-dose methotrexate is employed as a therapeutic intervention for a diverse range of malignant conditions including leukemia, lymphomas, and osteosarcoma. Hypoalbuminemia also decreases the methotrexate clearance leading to increased toxicity. Objective: To determine the frequency of side effects among patients receiving high dose methotrexate therapy based on baseline albumin levels. Study Design: A quasi-experimental trial was conducted at the Pakistan Institute of Medical Sciences, Islamabad, from January 1, 2023, to July 31, 2023. A total of thirty-four children receiving HDMTX were enrolled in the study. Albumin level, grade of liver toxicity, renal function tests, gastrointestinal and neurological toxicity, and mucositis were noted. Length of stay and methotrexate level at 24 hours were also noted. All the information was recorded in proforma.