The 27-year-old, of Foxglove Close, Southall, was jailed for 12 years, with an extension of five years and a minimum term of eight years, for a charge of preparation of terrorist acts.
He was sentenced to seven years each for offences of attendance at a place used for terrorist training and receiving weapons training, and received an 11-year term for a charge of possession of an article for terrorist purposes - all to run concurrently.
In his closing statement at Woolwich Crown Court on Friday, Justice Jeremy Baker discounted Khawaja's account maintaining that he was "returning through concern for his family and after becoming disillusioned with Islam."
He said he believed Khawaja "posed a significant danger to the public in the UK and abroad" and that an immediate custodial sentence was justified.
On January 26 last year, Khawaja left from Heathrow Airport and travelled to a training camp in Syria, the court heard. It was here that he joined 'Rayat al Tawheed', a group which became aligned with Islamic State.
Khawaja became a leading figure and "poster boy" for their promotion and recruitment to the jihadist cause.
The court was told how the group began posting violent propaganda online, in an attempt to recruit others. In response, the Metropolitan Police Counter Terrorism Command (SO15), working closely with MI5, launched an investigation.
Khawaja features in one of the group's promotional videos 'Five Star Jihad' where he is introduced as 'Abu Daigham'. The video presents a vision of daily life at the Rayat al Tawheed training camp, encouraging others to join them.
He is also seen in a disturbing video, posted on social media, which includes a bag of severed heads. He appears in the footage with his face covered, picking up one of the heads from the bag and showing it to the camera.
Justice Baker continued: "It is clear from your Facebook account that over the last few years you have been showing an increasing interest in Islamic jihadist material.
"By way of example, in 2011 you shared a video tribute to a Chechen mujahideen commander. In 2012, you shared a video, glorifying Islamic martyrs, and in 2013 you shared a jihadist video showing battle scenes from the war in Syria."
He added: "By the beginning of 2014 you had become sufficiently radicalised in your views about Islam that you decided to leave your home and travel to Syria in order to train as a terrorist. Something, which you subsequently informed your sister, you had been planning for a long time.
"I have seen nothing which would lead me to believe that your interest in travelling to Syria was motivated by any genuine humanitarian concern for the local population, as opposed to support for jihad and the Islamic state."
In May 2014, the terrorist group claimed Abu Daigham al-Britani (Khawaja) had been killed. This news of his death was picked up and reported by the British media.
However, Khawaja was not dead. He was in fact making his way back to the UK, the court heard.
On 3 June 2014, Khawaja and his cousin, Tahir Bhatti, were arrested by SO15 officers as they entered the UK at Dover Port in a hire car. Bhatti had driven to Serbia to collect Khawaja and bring him back to the UK.
Commander Richard Walton, Head of the SO15 Counter Terrorism Command said: "The images and video of Khawaja in Syria are horrific and deeply disturbing. He was a senior figure in Rayat al Tawheed, a group aligned to the Islamic State terrorist group that celebrated its terrorist acts through social media back to the UK.
"Khawaja chose to become a terrorist, engaged in weapons training in a terrorist training camp and faked his own death in order to conceal his entry back into the UK.
"This sentence sends a powerful message to those who plan or prepare acts of terrorism overseas or here in the UK.
"We have seen how parts of Syria have become lawless, where murder, torture and crimes against humanity are becoming almost routine.
"One of the best ways we can respond to these crimes is to convict terrorists through the rule of law."
Khawaja's cousin, Bhatti, 45, of Clarke Way, Watford, and friend Asim Ali, 33, of Spikes Bridge Road, Ealing, were both jailed for 21 months.
Bhatti had previously pleaded guilty to assisting an offender and Ali admitted entering into a funding arrangement for the purposes of terrorism.
Ali had withdrawn £300 which he had given to Khawaja in the knowledge that that money would likely be used to commit acts of terrorism.