Adjusted pre-tax profit for the 27 weeks to 3 July was £66.9m, as against £47m for the same period last year.
Trinity Mirror took control of Local World last October in a deal worth £220m, making it the UK's largest regional news outlet.
The acquisition more than offset losses incurred by the group's failed national daily the New Day, which closed in May.
It had hoped to sell about 200,000 copies a day, but sales were reportedly no more than 40,000 by the end of its nine weeks in existence.
"I am pleased we delivered another strong performance despite the challenging print environment," said Trinity Mirror chief executive Simon Fox.
"We are already seeing the benefits from our acquisition of Local World last year and continue to tightly manage the cost base across the group."
Mr Fox told the BBC that "Local World brought with it sales and profits and a huge number of respected titles".
The Trinity boss said the company's focus was on digital, as "there may well be a time when there are no papers". But he added: "I hope and think papers have a long life ahead of them - at least 10 years."
Local World was formed from a merger in 2012 of Daily Mail & General Trust's Northcliffe Media, and Iliffe News & Media. The takeover means that Trinity Mirror now publishes more than 200 titles.
In its results statement, the company unveiled a £10m share buyback, equivalent to about 5% of its market capitalisation.
It said it would also pay at least half the amount it spends on the share buyback, up to a maximum of £7.5m, on extra pension contributions.
Newspaper firm Trinity Mirror has seen half-yearly profit rise 42.3% after it bought local paper group Local World.