The susceptibility of surface-modified wood, surface-modified acetylated wood and acetylated wood to mold and blue stain fungi was investigated. The surface modifications were based on fluorinated and non-fluorinated silicone nanofilaments for increased hydrophobicity. Results showed an increased mold resistance of the surface-modified superhydrophobic wood with mold appearing later or with less intensity on the modified surfaces than on the untreated wood in accelerated mold chamber tests due to the increased water resistance of the samples. All acetylated wood samples exhibited good mold resistance as the available water in acetylated wood was reduced. The surface modifications on acetylated wood had a slightly negative effect on mold resistance due to side effects from the modification. The surface-modified wood showed high blue stain fungi coverage, whereas almost no blue stain fungi were observed on the acetylated wood and surface-modified acetylated wood. The surface-modified superhydrophobic wood showed high mold coverage after conditioning in a high-humidity environment or after exposure to UV irradiation. Meanwhile, the acetylated wood and surface-modified superhydrophobic acetylated wood showed a small amount of mold coverage in these conditions. © 2023 The Authors