It was developed as a land-based derivative of the Ha 139 seaplane during the late 1930s; considerable attention was paid to the needs of the German flag carrier Luft Hansa, who sought such an aircraft to work its transatlantic airmail service.

It was evaluated by Luft Hansa, but no regular airmail services were ever operated by the Ha 142, a fact that can largely be attributed to the outbreak of the Second World War.

In response to the conflict, two of the existing aircraft were converted for their use by the Luftwaffe, being outfitted with a new glazed nosecone and armed with multiple defensive machine guns and a modest bombing capacity.

The Ha 142 was also intended to be operated on transatlantic airmail runs, although it is uncertain whether it was interest within the German flag carrier Luft Hansa or within the design team itself that had primarily driven the project's launch.

[1] The center section of the wing was strengthened by a typical Blohm & Voss cross-girder which consisted of a large-diameter pipe.

[2] An extended nose section was fitted that had extensive glazing (resembling the Heinkel He 111H-6 in this respect) while the addition of a sixth crew member was necessitated via the installation of various navigation aids and military radio apparatus.

Furthermore, provisions for its use as a bomber were also incorporated, such as the installation of an ordinance compartment within the fuselage, although the aircraft had a relatively small payload capacity of 400 kg.

[2] Multiple defensive armaments were also added, including a 7.92 mm/.312 in MG 15 machine gun in the nose, twin-beam positions, a ventral cupola, and an electrically-powered dorsal turret.

Specifically, two were flown in the aerial reconnaissance role by KüFlGr 406 and 2./AuKlGr ob d L, while the other two were used for logistical support with KGzbV (Special combat team) 108; it is also recorded that two Ha 142s were briefly operated in the troop transport capacity with KGrzbV 105.