Peter Edwards, who worked as a senior paramedic, was dismissed in February 2022.
While securing a 14-year-old patient to a trolley to take him to West Suffolk Hospital, Edwards was hit in the face by the patient, who had reportedly consumed excess alcohol.
The employment tribunal heard that the claimant's "instantaneous reflex reaction" was to protect himself for further harm.
Following the incident, the paramedic was suspended pending an investigation and eventually dismissed for gross misconduct for physically assaulting a patient.
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Katie Hodson, head of employment at law firm SAS Daniels, said there were failings in the way the ambulance service handled the allegations.
Speaking to HR magazine, she said: “The employee was dismissed for gross misconduct based on witness evidence from a colleague.
“However, the tribunal found that the colleague provided inconsistent multiple statements and the employer did not take any reasonable steps to consider the totality of his evidence and weigh up his credibility as a witness.”
The appeal was also mishandled, as Edwards was given only 10 minutes notice that his colleague would be there to give evidence.
The tribunal judge labelled this as “obvious unfairness”.
Hodson said: “It is important that when dealing with third party complaints and carrying out an investigation, employers do not forget that the subject of the complaint is entitled to a fair process.
“A failure to carry out a fair and reasonable investigation may not only result in a finding of unfair dismissal, but also an uplift to the compensation.”
Libby Payne, employment partner at law firm Withers, said employers must balance the seriousness of third-party complaints with employee wellbeing.
Speaking to HR magazine, she said: “Employers should try to keep internal disciplinary processes separate from any process to resolve a dispute with a third party.
“Internal processes are confidential, and the third party should not automatically be informed of the details of any process that is happening or the outcome of that process.”
She said employers should make sure both employees and third parties can easily report any concerns and trust they will be addressed, particularly in industries like emergency care where employees are at higher risk of abuse.
She added: “Employees who are consistently on the receiving end of abuse from customers can be seriously affected in terms of their health and employment, potentially giving rise to liability for employers.
“Intervening early in such issues can reduce the impact on the employee and the risk to the employer."
An East of England Ambulance Service spokesperson said they will not appeal the outcome of the tribunal: “We respect the outcome of the employment tribunal which was not in agreement with our decision to dismiss the now ex-employee.
“The safety of our patients is a top priority for the trust and every allegation against a staff member around professional conduct with patients is investigated thoroughly.”