The bonus-point victory puts Sale in second place in Pool Five behind leaders Brive, and their home clash with the French side already has the look of a group decider.
Fly-halves Valentin Courrent and Nick McLeod swapped early penalties before the home side took advantage of a yellow card shown to Agen lock Damien Lagrange.
The Sharks made their one-man advantage count in emphatic fashion with quick tries from Tom Brady and skipper David Seymour to stretch their lead to 20-6.
Courrent's third penalty on the stroke of half-time made it 20-9, but after the break Brady crossed for his second try before scrum-half Cillian Williams scored the home side's fourth try for the vital bonus point.
Agen's replacement centre Jamie Robinson, the former Wales international, and Tongan number eight Opeti Fonua then scored tries for the visitors to close the gap, but a late try from Scott Mathie sealed a comfortable Sale win.
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The entire All Blacks apparel line has been updated for 2013/14. Check out the New Zealand All Blacks polo.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Gilbert Blitz 8S rugby cleat is a great cleat at a great price of $69.99. Get a new pair of cleats today.
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
The All Blacks Performance t-shirt is black with hints of blue from the training jersey. Very Cool.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.