A study of 4,000 young men and women found that beauty boosted pay cheques more than intelligence.
Those judged to be the easiest on the eye earned up to 10 per cent more than their less attractive friends and colleagues.
Applied to the average salary of £25,000, the 'plainness penalty' would make a difference of £2,500 a year - or around £50 a week.
It is unclear what is behind the phenomenon but it may be that beauty breeds confidence. The self-assured may appear to be doing better than they are and will have fewer qualms about badgering for a pay rise.
Researcher Jason Fletcher, of Yale University in the U.S., rated the attractiveness of the young men and women. Just over half were judged average, while 7 per cent were felt to be very attractive and 8 per cent were judged unattractive or very unattractive.
Plainness penalty: Beautiful people, like Birmingham City's MD Karren Brady (left) are paid more than less attractive colleagues, like Ugly Betty (right)
It is a blow for the Ugly Bettys and Plain Janes - research shows that good looks lead to better pay.
The volunteers also sat an IQ test and disclosed their salary. It became clear that pay scales were far from fair.
For instance, a 14-point increase on the IQ score was associated with a 3 to 6 per cent increase in wage. But being of above-average looks boosted pay by 5 to 10 per cent.
For a plain person to be paid the same as a very attractive one, they would have to be 40 per cent brighter, the journal Economics Letters reports.
Dr Fletcher said: 'The results do show that people's looks have an impact on their wages and it can be very substantial.'