Abstract <p>The study of reflection and transmission phenomena offers essential insights into the interior composition of structures. Reflection and transmission properties of plane waves in a fluid half-space (FHS) lying over a functionally graded porous piezoelectric half-space (FGPPHS) is examined in this paper. The progressive change in the functional characteristics is examined throughout the thickness dimension. When wave, incident from the upper fluid half-space strike the lower graded half-space, five waves are transmitted into the FGPPHS along with one reflected wave in the FHS. The comprehensive solution for constitutive equations is determined analytically. Expressions for the amplitude and energy ratios corresponding to reflected and transmitted waves are derived. Numerical analysis is done to investigate the influence of incidence angle, graded coefficients, frequency, and porosity on reflection and transmission properties, along with critical angles. Additionally, several materials are chosen for the FGPPHS, and their influence on material properties is analyzed. The selection of materials substantially influences the critical angle. The influence of porosity, frequency and grade parameters on leaky wave velocity is also examined. This study’s results offer substantial insights pertinent to multiple fields, including geophysics, acoustic technology, ocean acoustics, and non-destructive testing.</p>