William Stuart, 10, from Etchingham, East Sussex has autism and a condition called global developmental delay (GDD) and cannot speak.
His family said the stolen iPad was his only way of communicating and without it he is more isolated than ever.
Sussex Police has appealed for information to help find the iPad.
The theft of the device, which was loaded with communication software Proloquo, was discovered on Tuesday.
Two TVs and an Xbox 360 were also stolen from the family's home in Burgh Hill.
"The iPad was William's only form of communication with the outside world and with us in particular," said his father Alastair.
"He is becoming more anxious and closed and is expressing his frustration in terms of anger and crying."
Senior lecturer in special education Dr Amelia Roberts said that when someone with autism loses their means of communication it is a devastating change for them.
"People with autism don't cope with change very well so from his perspective his world will now be turned upside down," she said.

Many have headed for Praia do Norte in Nazare, Portugal, where Hawaiian surfer Garrett McNamara set a world record for the largest wave surfed in 2011.
The storm created huge swells in the sea off Scotland leading to warnings from the Coastguard and RNLI.
The swell off Nazare has been recorded at a maximum of height of 40ft (12m).
But South Devon-based website Magicseaweed.com, which provides surfers with swell charts and surf forecasts, said the swell grew in size as it neared the beach.
Three years ago, Mr McNamara caught a 78ft (23m) wave to beat the previous 2008 record by more than a foot.
The Atlantic storm hit Scotland late on Tuesday and during Wednesday. The Western Isles, Orkney and Shetland and parts of the north and west mainland coast were the worst affected.
Wave heights measured west of South Uist by the University of the Highlands and Islands peaked at about 49ft (15m) on Wednesday.
The storm started in the Arctic where it had rapidly developed in strength in a process known as explosive cyclogenesis, or what some scientists and forecasters refer to as a "weather bomb".
Pressure at the centre of the storm dropped quickly in the space of 24 hours as it passed by the south of Greenland on a strong jet stream running in excess of 230mph.
As well as Nazare, surfers have been in Bilbao, northern Spain, for a Punta Galea Big Wave World Tour surfing event. It has also benefitted from swells created by the storm.

A woman got out of the vehicle and an unknown man jumped in and took the car.
Police said it happened at Boucher Crescent in south Belfast at about 17:25 GMT.
Members of the public managed to stop the car but the man fled on foot.
A short time later a man in his 30s was arrested and remains in custody. The two children were unharmed.
The family of a disabled boy have spoken of their distress after burglars stole an adapted computer which they say is a lifeline for their son.
[NEXT_CONCEPT]
Some of the world's top surfers have been riding massive waves generated by the Atlantic storm that hit Scotland.
[NEXT_CONCEPT]
A man has been arrested after a car was stolen with two young children inside.