The Mercedes star believes that tinkering with the qualifying format, which has caused splits in the paddock and amongst fans as the world championship tries to boost its appeal, is detrimental to the sport.
The autosport.Com website and BBC reported that when asked if Formula One is "broken, lacking direction, or in rude health?", Hamilton replied: "I would probably say the first two you suggested."
But Hamilton then added: "I don't want to say too much, but I do agree with the first two things you said."
The three-pointed carbon structure is placed at the front of the car and is intended to prevent more driver fatalities.
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"Please no! This is the worst looking mod (modification) in Formula 1 history. I appreciate the quest for safety but this is formula 1, and the way it is now is perfectly fine," Hamilton wrote on his Instagram page.
The Halo was tried on track by Ferrari's Kimi Raikkonen on Thursday.
Demands to increase driver safety have intensified following the deaths of Jules Bianchi and IndyCar driver Justin Wilson last year.
However, the father of former F1 driver Bianchi, who died after colliding with a recovery vehicle at the Japanese Grand Prix in 2014, claimed the new measures don't go far enough.
"This is a step forward, but it does not solve everything," Philippe Bianchi told Canal Plus.
"In the case of Jules it would not have changed since it was the extremely violent deceleration that we know caused the damage to his brain.
"The version of this Halo system I saw this morning did not convince me and still needs to be improved."
The Halo won't be used for the upcoming season which starts at the Australian Grand Prix on March 20, but a meeting of the F1 Commission last week approved measures aimed at introducing it for the 2017 season.