The effect of pressure and phosphorus content on GaPxSb1 (-) (x) alloys in the zinc-blende structure, some of its electronic, optical and mechanical properties has been carried out. The variation of the studied properties such as energy band gaps, refractive index, high frequency dielectric constant, and elastic constants (C-11, C-12 and C-44) and their related properties such as bulk (B), shear (S) and Young (Y-0) moduli of the considered alloys with pressure has been investigated. We found that most values of the studied properties were sensitive to the composition parameter x from 0 to 1, and the applied pressure p from 0 to 12 x 10(9) Pa. Our calculations have been done using the empirical pseudo-potential method (EPM) coupled with the virtual crystal approximation (VCA) included the compositional disorder effect. A comparison between some of our calculated results and the available experimental data showed good agreement and excellent for the parent binary compounds GaP and GaSb which give a support for those of the GaPxSb1 - (x) ternary alloys. (C) 2015 Elsevier B.V. All rights reserved.