In Karlsruhe on 3 May 1842, Ernest married 21-year-old Princess Alexandrine of Baden. She was the eldest daughter of Leopold, Grand Duke of Baden, and Princess Sophie of Sweden, daughter of the deposed King Gustav IV Adolf of Sweden. Though he gave his consent, his father was disappointed that his first son did not do more to advance the concerns of Coburg. The marriage did not produce any issue, though Ernest apparently fathered at least three illegitimate children in later years.