Cox, who had 38 hit-outs and two goals in the Eagles' narrow loss to the Sydney Swans, received a total of seven votes from coaches John Worsfold and John Longmire, with Adam Goodes also earning seven votes for his last quarter heroics at Patersons Stadium.
Cox moved past last week's leaders Dane Swan and Corey Enright, who were out of the votes in Collingwood and Geelong's round three wins.
Western Bulldogs captain Matthew Boyd and Essendon skipper Jobe Watson both received perfect 10s from the coaches, pushing them into the top three overall.
Watson, who had 33 possessions, nine clearances and three goals in Essendon's big win over St Kilda, was one of seven Bombers to earn votes, with Saint Jason Gram preventing a clean sweep.
Three-time winner Gary Ablett earned his - and Gold Coast's - first votes for the season in the Suns' second match, while livewire Melbourne forward Liam Jurrah was recognised for his five-goal effort against the Brisbane Lions.
Round three votes
Collingwood v Carlton
9 Jarryd Blair (Coll)
9 Heath Shaw (Coll)
6 Jeff Garlett (Carl)
2 Travis Cloke (Coll)
2 Ben Johnson (Coll)
1 Michael Jamison (Carl)
1 Chris Judd (Carl)
Western Bulldogs v Gold Coast
10 Matthew Boyd (WB)
6 Gary Ablett (GC)
4 Daniel Cross (WB)
4 Robert Murphy (WB)
2 Josh Hill (WB)
2 Shaun Higgins (WB)
1 Dale Morris (WB)
1 Ryan Griffen (WB)
Adelaide v Fremantle
9 David Mundy (Frem)
7 Scott Thompson (Adel)
5 Nat Fyfe (Frem)
3 Stephen Hill (Frem)
3 Matthew Pavlich (Frem)
2 Bernie Vince (Adel)
1 Luke McPharlin (Frem)
Richmond v Hawthorn
9 Lance Franklin (Haw)
7 Josh Gibson (Haw)
6 Brad Sewell (Haw)
6 Jordan Lewis (Haw)
1 Luke Hodge (Haw)
1 Liam Shiels (Haw)
West Coast v Sydney Swans
7 Adam Goodes (Syd)
7 Dean Cox (WCE)
5 Jude Bolton (Syd)
4 Kieren Jack (Syd)
3 Nick Smith (Syd)
3 Quinten Lynch (WCE)
1 Shane Mumford (Syd)
Melbourne v Brisbane Lions
8 Liam Jurrah (Melb)
5 Jared Rivers (Melb)
5 Brent Moloney (Melb)
5 Luke Power (Bris)
4 Jed Adcock (Bris)
3 Mitch Clark (Bris)
Geelong v Port Adelaide
9 James Kelly (Geel)
8 Jimmy Bartel (Geel)
5 Joel Corey (Geel)
4 Joel Selwood (Geel)
2 Brad Ottens (Geel)
1 Mitch Duncan (Geel)
1 Paul Chapman (Geel)
St Kilda v Essendon
10 Jobe Watson (Ess)
6 Sam Lonergan (Ess)
4 Tom Bellchambers (Ess)
4 Dustin Fletcher (Ess)
2 Jason Winderlich (Ess)
2 Michael Hurley (Ess)
1 Heath Hocking (Ess)
1 Jason Gram (StK)
Leaderboard
22 Dean Cox (WCE)
20 Jobe Watson (Ess)
19 Matthew Boyd (WB)
17 Corey Enright (Geel)
17 Chris Judd (Carl)
17 Dane Swan (Coll)
15 Chris Dawes (Coll)
15 Brent Moloney (Melb)
14 Jude Bolton (Syd)
14 Marc Murphy (Carl)
