Abstract We studied the multiband properties of two ultraluminous X-ray sources (2CXO J225728.9−410211 = X-1 and 2CXO J225724.7−410343 = X-2) and their surroundings, in the spiral galaxy NGC 7424. Both sources have approached X-ray luminosities LX ∼ 1040 erg s−1 at some epochs. Thanks to a more accurate astrometric solution (based on Australia Telescope Compact Array and Gaia data), we identified the point-like optical counterpart of X-1, which looks like an isolated B8 supergiant (M ≈ 9M⊙, age ≈30 Myr). Instead, X-2 is in a star-forming region (size of about 100 pc × 150 pc), near young clusters and ionized gas. Very Large Telescope long-slit spectra show a spatially extended region of He II λ4686 emission around the X-ray position, displaced by about 50 pc from the brightest star cluster, which corresponds to the peak of lower-ionization line emission. We interpret the He II λ4686 emission as a signature of X-ray photo-ionization from the ULX, while the other optical lines are consistent with UV ionization in an ordinary He II region. The luminosity of this He++ nebula puts it in the same class as other classical photo-ionized ULX nebulae such as those around Holmberg II X-1 and NGC 5408 X-1. We locate a strong (5.5-GHz luminosity ν Lν ≈ 1035 erg s−1), steep-spectrum, unresolved radio source at the peak of the low-ionization lines, and discuss alternative physical scenarios for the radio emission. Finally, we use WISE data to obtain an independent estimate of the reddening of the star-forming clump around X-2.