Kesambi (Schleichera oleosa) is a plant belonging to the Sapindaceae familia. This study aims to determine the secondary metabolite compounds found in kesambi leaves through histochemical analysis and derivatives of active compounds in silico. Descriptive research method was conducted in January using samples of kesambi plants that grow on the island of Madura. Histochemical analysis was carried out by preparing fresh leaves through lower leaf incisions with secondary metabolite detection reagents (CuSO4, FeCl3, Wagner, Sudan III, AlCl3 & FeCl3 + NaCO3) then microscopic color changes were observed. In silico testing aims to determine the interaction of active compounds with ERα as a target for ER+ breast cancer therapy through molecular docking. Supporting software used is KNApSAcK, Pubchem, Pass Online, PDB ID, PyRx, PyMol and Chimera 1.14. The results showed that through histochemical analysis showed 6 secondary metabolite compounds namely terpenoids, flavonoids, alkaloids, tannins, lipophils and phenols. While in silico analysis (KNApSAcK) obtained active compounds namely scopoletin which is derived from phenol, (-)-beta-sitosterol, betulin, betulinic acid, lupeol, lupeol asetat, schleicheol 1, schleicheol 2, schleicherastatin 1, schleicherastatin 2, schleicherastatin 3, schleicherastatin 4, schleicherastatin 5, schleicherastatin 6 and schleicherastatin 7 which are derived from terpenoids. Based on the results of molecular docking, there are interactions of active compounds with 3ERT protein, namely lupeol acetate which is the most effective candidate for breast cancer drug with an affinity binding value of -8.3 and a root mean square deviation (RMSD) value of 1.588 Å and u.b of 2,219 Å and hydrogen bonds to amino acid residues SER518. Lupeol acetate compound is predicted to have activity as an Erα inhibitor against ER+ breast cancer. Keywords: Kesambi (Schleichera oleosa), histochemistry, molecular docking and ERα.