Eurostar said 12 trains were expected to run on Saturday in each direction between Paris and London, and up to six trains in each direction between Brussels and London.
This represents about half the normal traffic.
A daily train service to and from Disneyland Paris is also in operation.
Eurostar said travel times and waiting times would be longer than normal, but urged ticket holders to turn up as normal and said it would try to put them on the first available train.
It said passengers who had bought weekend tickets but had chosen not to travel because of the fire could apply for a full refund or exchange their ticket by returning to the place from which it was bought.
It was at that moment that we panicked the most, we imagined ourselves trapped there - we really were very lucky
Patrick Lejein, lorry driver
There were calm scenes at St Pancras International station in London, and few queues.
Passengers arriving back at St Pancras on Saturday said their journeys on Eurostar were slightly slower than normal. Some reported smelling smoke as the train went through the tunnel.
A number had booked ferries, having initially been told tunnel services may not resume at the weekend, but were able to board trains at the last minute.
Janet and Sean Larkin, from Epsom, Surrey, had to spend an extra night in Paris due to the tunnel closure.
Mrs Larkin said the train they boarded on Saturday was about 45 minutes late.
"When we got in the tunnel it really smelled of smoke - it was horrible. We are pleased to be back."
French firefighters working inside the Channel Tunnel
The tunnel was closed after fire broke out on a freight train about seven miles from Calais on Thursday. The 16-hour blaze was put out on Friday morning.
Thirty-two people on board were led to safety when the fire broke out. Fourteen had suffered minor injuries, including smoke inhalation.
Some of the lorry drivers involved in the incident have told how they escaped from an amenity car close to the fire.
Patrick Lejein, 50, from Bruges, Belgium, said: "We were all sitting in the club car at the front of the train when we heard two loud bangs, like explosions, and suddenly thick smoke swept through the carriage. Everything was exploding around us."
He said they were unable to open the door of their carriage: "One of the men on board - I think he was English - found a hammer from somewhere and were able to smash one of the windows and climb out."
"We escaped from the train through this window. It was at that moment that we panicked the most. We imagined ourselves trapped there. We really were very lucky."
British driver Leslie Boon, from Bridgend, south Wales, told ITN news that he thought "it was the end" and might not see his wife and three daughters again.
"It was just hell dealing with fire. Everyone started jumping up panicking and... then the wrong door opened.
"Someone opened the left hand door and I was pushed out of the wrong door and I ended up on the tracks.
"It was hot, very hot. I could not see nothing... I thought it was the end but I came to an exit."
He said he ran for about 1km (0.6 miles) up the main tunnel before he was intercepted by the emergency services.
The source of the blaze has not yet been identified but French officials say a lorry carrying chemicals, which is understood to have overturned on the freight train, was close to the seat of the fire.
It was carrying the chemical phenol, a toxic product used by the pharmaceutical industry.
French authorities are responsible for carrying out the investigation into the fire, although Kent Fire And Rescue Service said it would be supporting the inquiry.
The tunnel closure caused tailbacks on roads near the Eurotunnel terminal at Folkestone as dozens of lorries were forced to park on the M20 and other surrounding roads.
Kent Police say that the arrangements were still in force on Saturday morning, and that the M20 was still closed between junctions eight and nine.
I found out Eurostar had chartered a plane back to Stansted Airport and I was fortunate enough to get on it.
Andrew Fawcett-Wolf, Eurostar passenger
P&O Ferries have laid on extra services, but is advising passengers to re-book rather than just turning up at either Dover or Calais.
Motorists are still being advised to avoid the Dover area unless necessary although the slip road at junction 11a, leading to the tunnel, has reopened.
The Channel Tunnel has suffered several incidents since it opened to traffic in 1994 although only one - a fire in 1996 - caused injuries.
The fire caused £200m worth of damage and burned for more than five hours, wrecking the concrete lining and facilities over about half a mile of tunnel.
In August 2006, 34 people had to be led to safety after a fire broke out on a lorry being carried on a freight train.
Have you been affected by this incident? Are you a lorry driver waiting to travel through the tunnel? Have you been able to make alternative arrangements to get home? Send us your comments and experiences using the form below:
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