In 1622, Bernard married Gabrielle-Angélique de Verneuil, legitimised daughter of Henri IV and the Marquise de Verneuil, with whom he had a son, Louis-Charles-Gaston de Candale, and a daughter, Anne-Louise-Christine de Foix de La Valette d'Épernon. Gabrielle-Angélique died in 1627 (some say Bernard poisoned her) and in 1634 he married Marie Ducambaut, a niece of Cardinal Richelieu. It was not a happy marriage, as Bernard later conceived a life-long passion for a middle-class woman named Ninon de Lartigue, who exerted absolute power over him and to whom he gave enormous sums of money.
Like his father, Bernard made a career of the military. He was named Colonel-General of infantry and fought at the sieges of Saint-Jean-d'Angély and of Royan (1621) and at the attack of the pas de Suse (1629). On 15 May 1633, Bernard became a Chevalier du Saint-Esprit and in 1635 he was charged by Louis XIII with restoring the order which had been disturbed by lifting of taxes and religious passions. He fought in Picardy (1636), in Guyenne, and finally against the Spaniards, and repressed the Peasants' Revolt (Révolte des Croquants) in 1637.
Bernard de Nogaret de La Valette d'Épernon participated in the Siege of Luebeck and had accompanied Charles de Valois, Duke of Angoulême during the French Army's desperate retreat back to France. De la Valette knew perfectly well that their newly adopted flanking maneuver technique was the best—probably the only—way to get out of the trap the French army was in during the Battle of Ahrensbök. By the time they reached the Trave near Reinfeld, however, scouts reported that lead elements of a new army led by Gustavus Adolphus were advancing from Luebeck. About two miles past Oldesloe, another horseman jostled de la Valette's mount and forced the animal off the road, causing his mount to thrash de la Valette, who suffered a broken collarbone, several cracked ribs, and left lacerations and bruises over half his body before killing the animal with a pistol shot. At that point, he collapsed unconscious and was left for dead before being discovered and captured by four Swedish soldiers. De La Valette quickly convinced them to take him prisoner, as he had a good ransom.