The 2013 Tour champion, who will feature among the top favourites for the July 4-26 race, made his move 2.5 kilometres from the finish in the final climb to Valfrejus and never looked back.
He quickly swallowed fellow Briton Stephen Cummings (MTN Qhubeka), who had spent the day in the breakaway, and distanced yellow jersey holder Tejay van Garderen.
Team Sky rider Froome, who also prevailed in Saturday's uphill finish in St Gervais, beat another Briton, Simon Yates (Orica GreenEDGE), to take the day's laurels with an 18-second advantage.
At the end of Sunday's 156.5-km trek from St Gervais, Van Garderen was fourth, behind Rui Costa, both 18 seconds behind Froome.
Overall, Froome beat Van Garderen (BMC) by 10 seconds with Portugal's Costa (Lampre) in third place, one minute 16 seconds off the pace.
“The Tour de France is the big objective,” said Froome, who achieved the Dauphine-Tour double in 2013. “I think the team is ready and I think I'm almost ready. I'm really excited.
“If you take the race by its horns like that, stick to the plan, sometimes it pays off. I could not be happier right now.”
Van Garderen, fifth in the 2012 and 2014 Tours, told reporters: “Every race you go to you want to shoot for the top. I am certainly happy with second place and I am really happy with how I am stacking up to all of my Tour rivals. I think it is a good sign for July.”
Among Froome's main Tour de France rivals, defending Tour champion Vincenzo Nibali looked far from his best.
The Italian took 12th place, 4:32 behind Froome after being unable to follow the best in the climbs on Saturday and Sunday as well as in Thursday's fifth stage to Pra Loup.
Nibali, however, also looked under-par last year in the Dauphine before going on to smash his rivals on the Tour.
Spain's Alejandro Valverde (Movistar) finished ninth, 3:12 adrift. Exciting prospects Romain Bardet of France (AG2R La Mondiale) and Yates were sixth and fifth respectively.
Other Tour contenders were not racing the Dauphine, the most prestigious warm-up event for the three-week extravaganza.
Leading favourite Nairo Quintana (Movistar) of Colombia and double Tour winner Alberto Contador (Tinkoff-Saxo) of Spain, who won last month's Giro d'Italia, will take part in La Route du Sud in France next week.
Frenchman Thibaut Pinot (FDJ), third in last year's Tour, is riding the Tour de Suisse where he is among the leaders after two stages on Sunday. – Reuters
Original source: Froome sends warning to TDF rivals