Bulk reactions of phenolic compounds (bisphenol-A and α,ω-diphenol oligosulfone) or thiols (thiophenol and bis(4-mercaptophenyl)sulfide) with bisoxazoline coupling agents, namely 2,2'-(1,3-phenylene)bis(2-oxazoline) (mbox), 2,2'-(1,4-phenylene)bis(2-oxazoline) (pbox), and 2,2'-(2,6-pyridylene)bis(2-oxazoline) (pybox), were carried out in the bulk at 140-240°C. The reactions were followed by viscosimetry, size exclusion chromatography, and ¹H- and ¹³C-NMR spectroscopy. The phenol/bisoxazoline bulk reactions at 240°C required the presence of sodium methoxide catalyst. Bisoxazoline pybox gave the best results in this case. Thiol and dithiol/bisoxazoline reactions were faster and did not require any catalyst. High-molar-mass polymers were obtained within 5 min at 200°C while using bis(4-mercaptophenyl)sulfide (BMPS) and any of the bisoxazolines. The NMR spectra of model compounds and polymers were fully assigned, showing that the oxazoline/phenol and oxazoline/thiophenol (tph) polyaddition reactions proceed in the expected way, without any noticeable side reaction. All polymers were amorphous and displayed good thermal stability. Bisoxazolines were also used as coupling agents for the preparation of copolymers of BMPS and α,ω-dicarboxy polyamide-12 and for the preparation of polysulfone-polyamide-12 block copolymers.