Labour has hailed its latest by-election win as a "stunning result" - despite the Scottish National party (SNP) nearly doubling its share of the vote.
Iain McKenzie took 15,118 votes to 9,280 for the Scottish National party's candidate Anne McLaughlin, who finished in second.
The 5,838 majority was significantly less than the 14,416 advantage held by 44-year-old former MP David Cairns, whose death earlier this year triggered the poll.
After the nationalists came within 500 votes of taking the Scottish parliamentary seat in May's Holyrood elections the result is being viewed as a Labour success, however. Both sides had expected Labour to win by a far slimmer majority of just a few hundred votes.
"With a result like this I think we can safely say the SNP bandwagon has ground to a halt. Labour won this election because we listened hard and took nothing for granted," Mr McKenzie said.
"This is the start of Labour's fightback and there will be a lot more listening to do over the coming months and years."
Ms McLaughlin insisted she was "thrilled" to have cut Labour's majority by more than half, however.
"Obviously for us to cut their majority by so much, several thousand people voted SNP no doubt for the first time, so I'm really pleased that so many people took that step and will continue to vote for us," she said.
The result has been welcomed by Labour leader Ed Miliband, who would have been rocked by a shock defeat. Labour has held the Inverclyde seat for the last 80 years.
Instead pressure now grows on the Liberal Democrats, whose share of the vote collapsed by over ten points to just 2.2%.
The Lib Dem candidate took just 627 votes, compared to the Scottish Conservatives' third-placed 2,784. The Tories' share of the vote also fell, however.