We analyze the extension of the Minimal Supersymmetric Standard Model which includes extra Y = (0, ±1) supersymmetric triplets with a global SU (2) L ⊗ SU (2) R symmetry spontaneousy broken to the custodial SU (2) V by the vacuum expectation value of the neutral scalar components of doublets and triplets. The model is the supersymmetrization of the non-supersymmetric model introduced long ago by Georgi and Machacek where the ρ parameter is kept to unity at the tree-level by the custodial symmetry. Accordingly the scalar sector is classified into degenerate SU (2) V multiplets: singlets, triplets (including the one containing the Godstone bosons) and fiveplets. The singly and doubly charged chiral superfields play a key role in the unitarization of the theory. The couplings of the Standard Model-like Higgs to vector bosons (including γγ) and fermions, and the corresponding Higgs signal strengths, are in agreement with LHC experimental data for a large region of the parameter space. Breaking of custodial invariance by radiative corrections suggests a low-scale mechanism of supersymmetry breaking.