Frank's grandfather was Thomas Szécsényi, who rose to prominence during King Charles I's war against the oligarchs and received numerous land donations thereafter.

In the next year, now as magister, he led one of the Hungarian auxiliary troops in Italy to provide assistance to the Carraresi (or da Carrara) family and their paterfamilias Francesco I, Lord of Padua, who fought a fruitless war against his powerful neighbor, the Republic of Venice, also a major enemy of Louis I.

[8] The Szécsényi brothers were one of the earliest domestic partisans of Sigismund of Luxembourg, who arrived to Hungary to validate the marriage agreement with Queen Mary.

[9] After the queens' capture and imprisonment, Sigismund' influence grew which reached its peak at the rescue of Mary and his coronation as co-ruler on 31 March 1387.

For his loyalty, Szécsényi was transferred to the rich urbanized Upper Hungary, where he was installed to the positions of ispán of Zólyom, Hont and Nógrád Counties, serving there until 1390.

Since the Angevin age, the Saint Ladislaus legend provided the subjects for numerous murals painted in medieval churches in Hungary.

As donator, Szécsényi ordered the preparation of murals in the churches of Rimabánya, Karaszkó, Kiéte and Rimabrézó (today Rimavská Baňa, Kraskovo, Kyjatice and Rimavské Brezovo in Slovakia, respectively),[11] which depict Biblical scenes or details from the Ladislaus legend.

[15] Sigismund began to prepare a war against the Ottoman Empire since their Serbian invasion in 1389, which gradually revalued the role of Transylvania as a staging military area for recruitments and border defense.

As a result, the king replaced the relatively militarily inexperienced Emeric Bebek with his faithful soldier Frank Szécsényi to the dignity of Voivode of Transylvania in October 1393.

[16] After a brief visit in December 1393, Szécsényi arrived to the province to stay permanently by early May 1394 from the Diet in Buda, where received instructions from Sigismund.

Szécsényi sent a courtly knight Gregory Bethlen to Wallachia to negotiate with Mircea I, who maintained close relations with Sigismund, relying on their common interest in the struggle against Ottoman expansion.

[17] After Mircea had to retreat to Hungary following Bayezid's invasion, Sigismund moved to Torda (today Turda in Romania), where Szécsényi convened a general assembly in December 1394 to proclaim and organize insurrectio, the nobles' "uprising" against the Ottomans.

After the emergence of the Kanizsai League and the killing of Stephen Lackfi and his followers in the Bloody Sabor of Križevci, Sigismund appointed his most loyal men to the court dignities, including Szécsényi, who became Judge royal in November 1397.