The 2003 World Cup winner admitted speeding when stopped in his Range Rover on the M5 in Somerset as he returned to Leicestershire from his holiday home in Devon around 10pm on 13 August.
His wife and two children were also in the vehicle. Johnson, who stepped down as England head coach after the 2011 Rugby World Cup, was banned for driving for 49 days, fined £800 and instructed to pay an £80 victim surcharge plus £35 costs.
Defending Johnson, Stephen Gooden told Taunton Magistrates’ Court: “He admitted his guilt at the first available opportunity and co-operated with police.
“When he was stopped, the traffic was light and he was in a very powerful vehicle.”