A spokesman for the bank said that the company had become aware of the issue after the print run had taken place and that 22,600 statements of the 35,000 batch had been affected.
He said "the computerised system showed there had been a misfeed". He said there was an investigation into what had happened but that the bank had taken "full responsibility for the error" and declined to name the printer.
The error showed another customer's name, account number and spending habits on the second and third pages of affected statements, which Santander described as "embarrassing" but "a one-off incident". It maintained that the mix-up did not add to any risk of fraud.
Santander has around 5m UK customers. It said it had informed the FSA of the incident and taken steps to correct the issue.
Earlier this year a similar printing error caused problems for HMRC when tax credit renewal forms were mixed up, revealing details of up to 50,000 claimants.
And in February, Skipton Building Society customers experienced a similar "printing error" issue.
'Misfeed' mixes up thousands of Santander customer statements
Thousands of UK customers of Spanish banking giant Santander received statements on which other customers' information had been printed due to a 'misfeed'.
