The ad, part of a campaign by Cycling Scotland, said in a voiceover: "Not a lot of people know this but you should treat a cyclist the way you treat a horse ... slow down, treat them with care and give them their space on the road."
But five viewers complained that the ad was irresponsible and harmful because it showed a cyclist without a helmet or any other safety attire.
Cycling Scotland told the Advertising Standards Authority (ASA) that wearing a cycling helmet was not a legal requirement in Scotland but a personal choice for the individual - a fact it considered was reflected in the ad
with footage of
various cyclists both with and without helmets.
The ASA acknowledged the ad was primarily aiming to encourage motorists to take care when driving near cyclists.
But it noted that the cyclist in the final scene was not wearing a helmet or any other safety attire and appeared to be more than half a metre from the parking lane.
Cycling Scotland chief executive Ian Aitken said: "We are disappointed with the adjudication of the ASA Council and the statement that future ads should always feature cyclists wearing helmets.
"Our guidance on the issue of helmets and safety attire for adults on bicycles mirrors the legal requirements set out for cyclists in the Highway Code."
Transport Minister Keith Brown said the issue was a matter for Cycling Scotland.