The global pharmaceutical industry has seen significant growth, with peptides, which are amino acids linked by amide bonds, becoming increasingly important. Peptides offer a well-tolerated safety profile and specificity, making them valuable tools in addressing unmet medical challenges. Insulin is a well-known example of a peptide used in medicine. Peptides are considered excellent complements or alternatives to small molecules and large antibodies. Currently, around 100 peptide drugs are available globally, with over 150 in clinical development and an additional 400–600 in preclinical studies. Peptides play a crucial role in cancer research and treatment, contributing to improved survival rates for cancer patients. The United States Food and Drug Administration (FDA) has approved numerous peptide-based drugs for cancer therapy. These peptides exhibit high specificity, permeability, and target engagement, and they can function as agonists or antagonists. They are used in various forms, including imaging agents and dual-purpose theragnostic agents. This review analyzes FDA-approved peptide-based anticancer drugs, focusing on their chemical structures, therapeutic targets, mechanisms of action, development journeys, administration routes, and side effects. Key areas discussed include: 1. **Prostate-Specific Membrane Antigen (PSMA) Peptide Antagonists**: These peptides selectively bind to PSMA-producing cells and can be used for imaging or treatment. Examples include 68Ga-PSMA-11, Piflufolastat F 18, Lutetium 177 Lu Vipivotide Tetrazetan, and Flotufolastat F 18. 2. **Peptide Receptor Radionuclide Therapy (PRRT)**: PRRT uses cyclic octapeptides radiolabeled with radionuclides to target neuroendocrine tumors. Examples include Depreotide, 68Ga-DOTATATE, [177Lutetium]Lu-DOTA-TATE, 68Ga-DOTATOC, and 64Cu-DOTATATE. 3. **Somatostatin Analogs**: These peptides inhibit the secretion of hormones that contribute to tumor growth. Examples include Octreotide, Lanreotide, and others. 4. **Antibody Drug Conjugates (ADCs)**: ADCs deliver highly potent cytotoxic drugs to therapeutic targets. Examples include Enfortumab Vedotin-Ejfv, Polatuzumab Vedotin-Piq, Fam-Trastuzumab Deruxtecan-Nxki, Belantamab Mafodotin-Blmf, Tisotumab Vedotin-Tfv, and Loncastuximab Tesirine-Lpyl. 5. **Gonadotropin-Releasing Hormone (GnRH) Analogs**: These peptides are used to treat prostate cancer by reducing testosterone levels. Examples include GoserelinThe global pharmaceutical industry has seen significant growth, with peptides, which are amino acids linked by amide bonds, becoming increasingly important. Peptides offer a well-tolerated safety profile and specificity, making them valuable tools in addressing unmet medical challenges. Insulin is a well-known example of a peptide used in medicine. Peptides are considered excellent complements or alternatives to small molecules and large antibodies. Currently, around 100 peptide drugs are available globally, with over 150 in clinical development and an additional 400–600 in preclinical studies. Peptides play a crucial role in cancer research and treatment, contributing to improved survival rates for cancer patients. The United States Food and Drug Administration (FDA) has approved numerous peptide-based drugs for cancer therapy. These peptides exhibit high specificity, permeability, and target engagement, and they can function as agonists or antagonists. They are used in various forms, including imaging agents and dual-purpose theragnostic agents. This review analyzes FDA-approved peptide-based anticancer drugs, focusing on their chemical structures, therapeutic targets, mechanisms of action, development journeys, administration routes, and side effects. Key areas discussed include: 1. **Prostate-Specific Membrane Antigen (PSMA) Peptide Antagonists**: These peptides selectively bind to PSMA-producing cells and can be used for imaging or treatment. Examples include 68Ga-PSMA-11, Piflufolastat F 18, Lutetium 177 Lu Vipivotide Tetrazetan, and Flotufolastat F 18. 2. **Peptide Receptor Radionuclide Therapy (PRRT)**: PRRT uses cyclic octapeptides radiolabeled with radionuclides to target neuroendocrine tumors. Examples include Depreotide, 68Ga-DOTATATE, [177Lutetium]Lu-DOTA-TATE, 68Ga-DOTATOC, and 64Cu-DOTATATE. 3. **Somatostatin Analogs**: These peptides inhibit the secretion of hormones that contribute to tumor growth. Examples include Octreotide, Lanreotide, and others. 4. **Antibody Drug Conjugates (ADCs)**: ADCs deliver highly potent cytotoxic drugs to therapeutic targets. Examples include Enfortumab Vedotin-Ejfv, Polatuzumab Vedotin-Piq, Fam-Trastuzumab Deruxtecan-Nxki, Belantamab Mafodotin-Blmf, Tisotumab Vedotin-Tfv, and Loncastuximab Tesirine-Lpyl. 5. **Gonadotropin-Releasing Hormone (GnRH) Analogs**: These peptides are used to treat prostate cancer by reducing testosterone levels. Examples include Goserelin