Extensive studies of hidden spin polarization have established a broad class of hidden phenomena in quantum materials. Here, we introduce the hidden piezo-Hall effect, in which strain induces finite anomalous Hall conductivities (AHCs) in individual sectors while the global AHC remains zero. At zero strain, neither the full system nor its sectors exhibit an anomalous Hall effect (AHE). Under uniaxial strain, however, opposite sector AHCs emerge while their sum remains canceled. We establish this effect for a d-wave hidden altermagnet using a tight-binding model and first-principles calculations for the experimentally synthesized material RbV₂Te₂O. Rotating the strain direction from the x to the y axis reverses the signs of the sector AHCs without generating a net Hall response. The same symmetry mechanism may also give rise to hidden piezomagneto-optical, piezo-thermal Hall, piezo-Nernst, and piezo-Ettingshausen effects. Our work extends hidden physics to strain-controlled transport and identifies RbV₂Te₂O as a promising candidate for experimental verification.