That was what official data showed on Wednesday (December 13).
Gross domestic product - or GDP - fell by 0.3% from September.
Britain's Office for National Statistics said exceptionally wet weather may have had an impact.
Britain's huge services sector shrank by 0.2% in October, while manufacturing and construction also contracted.
Analysts had expected no change in October's GDP.
It was the first time since July that GDP had shrunk on a month-by-month basis.
October's performance will likely test the Bank of England's resolve to stick to its tough anti-inflation line.
The central bank is currently against cutting interest rates from their 15-year high.
And it is widely expected to keep its Bank Rate at 5.25% in an announcement due on Thursday.
Markets also believe it will signal again it isn't close to cutting rates as it tries to ensure Britain's high inflation rate of 4.6% is brought under control.
Prime Minister Rishi Sunak and finance minister Jeremy Hunt have promised to speed up growth.
But no big pickup is expected before an election Sunak must call before January 2025.
