A total of 28 motorbikers died – 12 more than in 2020 and three more than in 2019, Transport Scotland reported.
Serious injuries among motorcyclists also increased, from 241 in 2020 to 275, with total casualties, including minor injuries, up 8 per cent to 450.
The increases came despite road deaths overall falling by two to 139 – the lowest since records began.
There was also a slight increase in pedestrian deaths, from 34 to 37, and while car deaths were down from 71 to 56, serious injuries increased from 620 to 701.
Serious injuries overall were up 65 to 1,596.
Transport Scotland said the figures were affected by a second Scotland-wide Covid lockdown between January and April, which reduced traffic.
Neil Greig, the Scotland-based policy and research director of motoring group IAM RoadSmart, said: “The real concert here is that we seem to be moving back towards the flatlining of road death numbers we have seen over the last decade.
"There are still no signs of substantial changes to really start bringing road deaths down again.
"Motorcycle injuries are a major worry but IAM RoadSmart are working with the Scottish Government through its new task force to prioritise actions.
"These numbers show how important that work is becoming.”
Transport minister Jenny Gilruth said: "The statistics confirm that for another year, overall road casualties on Scotland's roads are at the lowest levels since annual records began in 1950.
"However, like the figures for 2020, we should remember that the 2021 casualty numbers will be affected by the Covid-19 pandemic and the associated changes in travel.
"Whilst it's no surprise that with fewer car trips during the second national lockdown we're seeing fewer road casualties, prior to the pandemic road casualties in Scotland had been showing a clear, ongoing reduction and we must continue our hard work in this area as travel behaviours return to normal.
"One death on Scotland's roads is one too many.
"The fact that road casualties are at historically low levels means very little to those who have sadly lost friends and loved ones in tragic circumstances."