Magnetization and muon spin relaxation or rotation (µSR) measurements have been performed to study the superconducting and magnetic properties of Sr3Ir4Sn13. From magnetization measurements the lower and upper critical fields of Sr3Ir4Sn13 are found to be 81(1) Oe and 14.4(2) kOe, respectively. Zero-field µSR data show no sign of any magnetic ordering or weak magnetism in Sr3Ir4Sn13. Transverse-field µSR measurements in the vortex state provided the temperature dependence of the magnetic penetration depth λ. The dependence of λ −2 with temperature is consistent with the existence of single s-wave energy gap in the superconducting state of Sr3Ir4Sn13 with a gap value of 0.82(2) meV at absolute zero temperature. The magnetic penetration depth at zero temperature λ(0) is 291(3) nm. The ratio ∆(0)/kBTc = 2.1(1) indicates that Sr3Ir4Sn13 should be considered as a strong-coupling superconductor.PACS numbers: 74.25. Ha, 74.70.Dd, 76.75.+i Recently, ternary intermetallic stannide compounds, R 3 Ir 4 Sn 13 , where R = Ca, Sr, etc., have attracted renewed interest because of the coexistence of superconducting and charge density wave states and the possible presence of pressure induced quantum structural phase transitions.