Just over 46,000 vehicles were registered north of the border - a year-on-year increase of more than 2.7%.
However, UK sales increased by 5.3% to almost 519,000 - the strongest month recorded since 1999.
March is typically the biggest month, accounting for about a fifth of the year's car registrations.
Last month saw Vauxhall retain its position as market leader in Scotland, with more than 10,000 units sold.
The Vauxhall Corsa remained the most popular new car, while the Ford Fiesta had a strong month and moved into the number two spot for the year to date.
The figures were compiled by the Society of Motor Manufacturers and Traders.
Top Scottish sellers in March
1. Vauxhall Corsa 2,575
2. Ford Fiesta  1,772
3. Vauxhall Astra 1,249
4. Ford Focus 1,126
5. Volkswagen Polo 1,077
Source: SMMT
Scottish Motor Trade Association chief executive Sandy Burgess said: "All areas have experienced growth with the exception of Dumfries and Galloway and Strathclyde.
"The reductions however are minimal and with the fantastic growth on 2015 numbers elsewhere, we have come out of this critical sales period well ahead for the year to date.
"We have been aware of some dealers who were experiencing new vehicle delivery issues towards the end of the month, and this may well have had a small but noticeable negative effect.
"The rest of the UK continues to show stronger growth but as we have mentioned previously this may not all be down to sales with specific manufacturers and dealers taking tactical decisions on registrations."

The midfielder more than 150 appearances for Dale before joining Tranmere in 2012, and returned for a loan spell in 2013.
The 27-year-old was released by Carlisle United at the end of the 2015-16 campaign.
Rochdale began 2016-17 with a 3-2 home defeat by Peterborough on Saturday.
Find all the latest football transfers on our dedicated page.

The 33-year-old, leading after Friday's dressage, delivered a fault-free cross-country round on his mount La Biosthetique.
Jung won the Burghley and Kentucky titles and is hoping to seal the Rolex Grand Slam to earn the bonus.
Great Britain's challenge faltered, with Emily King eliminated.
She was second overnight but fell riding Brookleigh before Sunday's showjumping finale.
The 20-year-old shone in the dressage to raise hopes of becoming the youngest Badminton winner since 1973.
Instead it is Jung who will be centre stage as he attempts to become just the second winner of the Grand Slam, emulating Pippa Funnell in 2003.
"It's a long night, a big day, everything can happen," said Jung, an individual and team gold medallist at London 2012.
"For me, this is the best horse in the world. It is a wonderful feeling to ride such a good horse."
Jung remains on 34.4 penalty points, nine better off than compatriot Andreas Ostholt aboard So Is Et and 10.2 points ahead of Britain's Gemma Tattersall, who rides Arctic Soul, in third.
The cross-country challenge
Jung navigated all 33 obstacles over the 6,500m course with precision and finished well inside the optimal time - 11 minutes 58 seconds - at which competitors begin to incur time penalties.
It means he can afford to see two poles fall in Sunday's showjumping finale, assuming his closest rivals deliver blemish-free rounds.
"That horse is really amazing," added Jung. "He always listens to me and trusts in me."
In all, 27 of 75 horses failed to complete the course, set against the picturesque backdrop of Badminton House.
Organisers believe last year's cross-country attendance of 95,000 was comfortably bettered, with more than 100,000 people lining the track.
King's fall at the penultimate obstacle drew howls of concern from those watching and she was visibly upset.
The daughter of six-time Olympian Mary King is one of a number of Britons looking to position themselves for a place at the Rio Olympics.
Tattersall's third place overnight gives her a fine chance of improving on her best finish at Badminton - 16th last year.
Team GB hopefuls must hit qualifying standards on the horse they wish to take to the Games by 19 June, with a selection announcement expected in July.
Former world champion Zara Tindall and her mount High Kingdom have work to do, as they sit 24th in the field, but Oliver Townend and Izzy Taylor are eighth and ninth on Armada and Allercombe Ellie respectively.
New car sales in Scotland grew last month but at half the rate of the UK as a whole, according to motor traders.
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