In this work R3P=Se (R=Me, Et, n-Bu, t-Bu and Ph) were studied experimentally using NMR spectroscopy in solution and solid-state in combinaton with quantum chemical methods. The study shows that the NMR parameters of these phosphine selenides, such as δP, δSe, and 1JPSe, are sensitive to subtle changes in the electronic environment of the P and Se atoms. Consequently, phosphine selenides R3P=Se can serve as promising spectral probes for the detection and quantitative investigation of various non-covalent interactions. Additionally, the variation of R in phosphine selenides influences the observed NMR spectral parameters, primarily through effects such as π-backdonation and hyperconjugation, which have been observed experimentally and confirmed theoretically.