Janus was crowned in Santa Sophia on 11 November 1399, receiving all three crowns, of Jerusalem, Cyprus and Armenia, in one ceremony.

He is described by the chroniclers as tall and fat, physically strong, good-looking, with a slight blond beard; he had learning and good taste, but an Arab writer notes that he knew no Arabic.

While his father was still alive, negotiations had been begun to marry him to Mary of Navarre, daughter of Charles the Bad, but they came to nothing. Before 1401, however, he was married to Héloïse, a sister of the Duchess of Milan, Catherine Visconti, and one of the ten daughters of Barnabò Visconti.

From the beginning of this reign, the Kingdom continued to be vexed by the perennial difficulties with the Italian trading republics. Venice as usual was the less openly unpleasant of the two. She had her own differences with Genoa. On 16 June 1401, in order to avoid the quarrels which were continually arising, the Senate issued an order that no Venetian was to purchase any goods either at Famagusta or anywhere else in the island, which practically meant prohibiting all trade with it. The grievances of Venice against the Cyprus government were set forth by the ambassador John Canale, who was commissioned by the Senate on 19 August 1401. The agreements previously made by the Kings were not being observed; the sums due from the King to the Republic or to individual Venetians were not paid; the King's officers, especially the Viscount of Nicosia, did not respect the privileges granted to the Venetians.