Brett King told The Sun newspaper that a scan indicates there is "no evidence" that five-year-old Ashya King still has the tumour.
In August 2014, Brett and Naghmeh King pulled Ashya out of a Southampton hospital against the advice of doctors. The young boy had gone through two surgeries and was unable to eat or drink on his own or to speak. The Kings wanted Ashya to get proton beam treatment, which wasn't available in the U.K.
Following the issue of a European arrest warrant for the couple and a two-day international police search, the Kings were detained in Madrid and separated from their son.
However, extradition efforts were subsequently dropped, and a Spanish judge ordered the couple released.
The family then travelled in September to Prague, where Ashya began proton beam therapy. The treatment uses high-energy proton instead of x-rays to target cancer cells, and produces fewer side-effects, the BBC reported.
Brett King told The Sun that Ashya is now cancer free, recovering at a family home in Spain, and is starting to speak again.