Police were called by Tesco staff in Willesden, Brent last night when bargain hunters started gathering in huge numbers.
A police spokesman said that apart from the Willesden problems, they had to step in to calm crowds at supermarkets in Edmonton, Edgware and Surrey Quays.
No persons have been injured at any of the locations as a result of the overcrowding, and there have been no arrests.
Police have also had to organise crowd control at supermarkets in Manchester, Glasgow and Cardiff.
A spokesman for Tesco told the BBC that they expected Black Friday sales to beat their traditional Boxing Day bargain sales last year.
Its 24-hour stores began selling a minute after midnight, and extra staff have been laid on in some areas.
Black Friday - historically the big sales day in America that follows the Thanksgiving holiday - has been adopted by an increasing number of shops in the UK.
It was brought over by online store Amazon four years ago after internet shoppers noticed the US got the best deals.