Ronny Deila's side did not have it all their own way in Saturday's clash at Celtic Park, but Anthony Stokes' header on the stroke of half-time gave them the advantage.
Guidetti then netted his 10th goal in his last nine Celtic appearances when he finished Adam Matthews' cross from the right nine minutes after the restart.
James McPake saw an effort ruled out for offside shortly afterwards, but Dundee did hit back in the 58th minute when their own in-form striker, David Clarkson, became the first player in the club's history to score in each of his first seven games.
Celtic withstood the nervy ending, though, and they remain top on goal difference.
The other three sides in the top four were all victorious, with Inverness Caledonian Thistle staying level on points with Celtic thanks to a 3-1 win at home to Motherwell.
Motherwell looked good for at least a point when Henrik Ojamaa quickly cancelled out Billy McKay's opener in the first half, only for two goals in the space of seven second-half minutes from Marley Watkins and Josh Meekings to clinch the points for the hosts.
Third-placed Dundee United were also 3-1 victors at home to Kilmarnock, while Hamilton Academical - who are a point behind United in fourth - ended a run of four games without a win to pile more misery on lowly St Mirren with a 3-0 victory.
St Mirren remain off bottom spot on goal difference only, as 12th-placed Ross County slipped to a 2-1 loss at St Johnstone.
