​​On returning to the newly created Czechoslovakia in 1920, Jan Bejbl met his life partner, Antonie Chalupová, and they were married on 10 February 1923.

Jan became a member of the police at the Police Directorate in Bratislava. It was here that he met colleague Václav Král and postal clerk Václav Růta, a meeting that impacted the fate of both Jan and Antonie. After the breakup of Czechoslovakia in 1939, the family left their apartment in Bratislava and moved to Pilsen, meeting Václav Král again. Both men were actively involved in Resistance activities, which began to develop in Pilsen after the Nazi occupation of the Second World War.

Jan was involved in Operation Anthropoid, the famous assassination attempt on Reichsprotektor (Governor) Reinhard Heydrich, a key Nazi official from Germany. On 31 December 1941, Václav Král transferred paratroopers Jan Kubiš and Josef Gabčík to the Bejbls apartment in Pilsen. Jan arranged a connection to Prague, giving Kubiš and Gabčík the address of his old friend, Václav Růta.

​In April 1942, Jan actively participated in the preparation of Operation Canonbury, an Allied bombing raid on Pilsen’s Škoda armaments factory. After plans went awry, Jan and Václav Král hid paratrooper and radio operator, Oldřich Dvořák, in a Pilsen police prison cell for his protection. Resistance member Karel Čurda also appeared in Pilsen at this time.

On 16 June, Čurda reported to the Gestapo headquarters in Prague and gave up the addresses of all his supporters. On 17 June, employees of the Pilsen Gestapo arrested the families of Václav Král, Vojtěch Kučera, Aloise Hrdličková, and Jan Bejbl.  They were taken to Prague that same day, where they were interrogated at the Gestapo headquarters in Bredovská Street. In September 1942, they were transferred to the Gestapo prison in the Small Fortress of Terezín. There they awaited the verdict of the court-martial. On 29 September 1942, Jan Bejbl and Antonie Bejblová were sentenced to death. The sentence was carried out on 24 October 1942, with a shot in the back of the head. Antonie was shot at 08:44, the eighth among the group of women. Her husband was killed at 16:54.​