Cooking oil was poured into the water sometime overnight between Wednesday and Thursday last week.
Work continued over the weekend to clean-up the popular attraction on the seafront.
It meant the lido had to be completely drained and the basin was then chemically scrubbed and jet washed to ensure that all the oil was removed.
Council staff also had to check and, where necessary, clean the filters, pipework and a separate ballast tank to ensure that they were free from oil otherwise there was a risk that when the pool was refilled there was no remaining residue contaminating the water.
Once this was completed the pool was refilled with chlorinated water which took approximately two days.
Final checks took place this morning to ensure that the lido was clean and safe for families to use again.
Robert Francis-Davies, Swansea Council’s Cabinet Member for investment, regeneration and tourism, said: “I am pleased that we have been able to reopen the lido as soon as possible and I would like to thank those who worked extra hours immediately after the attack and over the weekend to make this possible.
“The lido is a very popular free attraction that we know is valued by young families.
“It remains frustrating that this was the second time we have been forced to shut the lido this year due to acts of vandalism and I sincerely hope it is the last.
“I would urge visitors to any of our attractions in Swansea to help us look after them so that they can continue to be enjoyed by all.
"If anyone sees anything suspicious we would urge them to report it immediately to available staff or to the police."