Stellaria ruderalis M. Lepší, P. Lepší, Z. Kaplan & P. Koutecký, a recently described allotetraploid species belonging to the S. media group, is reported here as new for the Iberian Peninsula (Barcelona and Gerona provinces) and the Balearic Islands (Mallorca). This species could be widely overlooked due to its overall similarity to S. media, and it is probably more widespread than currently known.