With the aim of reducing the affinity of poly(vinyl alcohol) (PVA) fibers to cementitious matrices and allowing the tailoring of crack-bridging behavior in strain-hardening cement-based composites (SHCC), a study was conducted, in which PVA fibers typically used in SHCC were subjected to different types of chemical surface modification. Alkyl chains were covalently bonded to the fiber surfaces via an acid-catalyzed acetalization with butanal diluted in sulfuric acid (H₂SO₄) and hydrochloric acid (HCl), respectively. X-ray photoelectron spectroscopy and contact angle measurements documented the successful treatment and the hydrophobic character of the modified fiber surfaces when compared to the as-received oiled and non-oiled fibers. The single-fiber pullout experiments showed that the butanal modification performed in H₂SO₄ yielded a considerably more pronounced reduction in chemical adhesion in comparison to butanal-HCl. However, the butanal-H₂SO₄ modification yielded no significant improvement in composite ductility, which could be traced back to the relatively low abrasion resistance of the fibers and to the resulting surface damage amplified by the higher extent of slippage. Furthermore, the milder butanal-HCl modification yielded a balanced fiber-matrix adhesion, resulting in SHCC with distinctly superior tensile properties.