The tennis ace stopped traffic as he saw the labradoodle running towards oncoming cars at the weekend then returned it to its startled owner.
Speaking at Wimbledon this morning as her son prepared for his next match, Judy Murray said her reaction was: "What you doing? You're on the way to Wimbledon and you're going to get run over."
She said the dog's owner was shocked to see who had saved her pet.
"Andy was sitting in the car and she just went, 'Oh my God'."
Ms Murray was remaining coy about rumours she is to star in Strictly Come Dancing, but made it clear who she would like as a partner.
She said: "Don't believe everything you read in the papers."
But when asked who she would like to have as a professional partner on the show, if she were to take part, she immediately said: "Artem."
Artem Chigvintsev is one of the programme's professional dancers.
Asked if she thought she would progress towards the final in the BBC show, she said: "I'm only going to be watching it on television."
The 54-year-old tennis coach is a big fan of Strictly and has posted comments about the dancers on her Twitter account.
She is believed to be in the advanced stage of talks to join the next series.
Surrounded by a press pack, Ms Murray, who was serving up coffee to fans in the queue, was asked why she would choose Chigvintsev.
"Because I think he is a phenomenal dancer and I love watching him dance," she said.
Echoing Sir Bruce Forsyth's catchphrase, she added: "He's my favourite."
Asked if Chigvintsev's toned chest had anything to do with her preference, she joked: "That's not bad either. That helps!"
Ms Murray was also coy about bookmakers closing betting on her son getting engaged to girlfriend Kim Sears during the tournament - and her views on the Scottish independence vote.
She volleyed back questions on both with "no comment" replies.
Murray Mania returned to Wimbledon today as Murray continued his bid for a second title at the All England Club.
The Scot faces Slovenian Blaz Rola on Court No.1 at 1pm in his second match of the famous tennis tournament.
Fans have been warned not to bring Thermos flasks to Wimbledon "for security reasons".
The flask ban means people will have to pay out £2.10 each time they want a cup of tea.
A tweet on the tournament's official Twitter account told people planning a trip to SW19 to check the list of prohibited items, adding: "Don't bring a thermos."
There were fewer people at Wimbledon yesterday than on the same day last year.
A total of 42,673 spectators attended - a decrease of 1,258 on day two last summer.
Attendance on the opening day this year was also down, with figures showing a decrease of 390 people on last year.