House prices were flat last month, compared with a monthly increase of 0.3 percent in September and a median forecast for a rise of 0.2 percent in a Reuters poll of economists.
Compared with October last year, prices rose by 4.6 percent, slower than September's increase of 5.3 percent and below a median forecast of 5.0 percent in the Reuters poll.
It was the slowest annual price growth since January, but Nationwide economist Robert Gardiner said it was still in line with rates since early 2015.
He said a 10 percent fall in housing market activity in recent months might be a lingering after-effect of April's introduction of a higher level of tax on properties bought by landlords and second homes.
Howard Archer, an economist with Markit HIS, said he expected house prices to fall by about 3 percent next year when Britain launches its negotiations to leave the European Union, probably adding to uncertainty about the economy.
Another mortgage lender, Halifax, said last month that British house prices rose at their slowest pace in more than three years in the three months to September.
But there have been other signs recently that the housing market slowdown might be bottoming out.
The Bank of England said on Monday that the number of mortgage approvals picked up in September. And the Royal Institution of Chartered Surveyors's house price index rose in September and August after slumping to a three-year low in July.
(Writing by William Schomberg; Editing by Tom Heneghan)