The Land Transport Authority said it would fine SMRT S$860,000 and SBS Transit S$250,000 over service disruptions.
SMRT will be penalised for four separate incidents, including the fire on cables near the Newton station that disrupted train service and affected 17,700 passengers on 13 February this year.
In a statement on Tuesday, LTA noted that in managing the incident, SMRT had committed several lapses, including detraining passengers at the Newton station rather than at an earlier station away from the fire.
The lapses were in breach of licence conditions and the penalty will be S$300,000 for the incident, the agency said.
It will also fine SMRT S$250,000 apiece for two incidents, namely, maintenance lapses that led to rail defects on the Circle Line in November 2012 and failure to apply proper procedures for track works at the Ulu Pandan Depot in December 2012.
For failing to launch the required number of trains for service at the Bukit Panjang LRT in the morning of 4 July this year, SMRT will be fined S$60,000.
In the case of SBS Transit, the transport authority said the company would be fined S$250,000 for the train service disruption on both bounds between Woodleigh and Punggol stations that affected about 54,900 passengers on 19 June this year.
The disruption was caused by a southbound train that stalled after departing Buangkok station. Investigations found that the train had stalled due to a short circuit caused by damage to a switch's insulation wires from abrasive rubbing.
"The LTA recognises that many of these incidents happened in 2012 and early 2013, and both SMRT and SBST have since taken appropriate measures to tighten their processes," Chew Hock Yong, LTA's chief executive said.
"We will continue to work together with both operators to put in place the necessary corrective measures," he added.
The total fines of S$1.11 million would be donated to the Public Transport Fund to ehlp needy families with transport fares, LTA said.