Ms Laurie, who worked previously for Burness and specialises in the oil and gas and financial services sectors, is joining as a partner. Ms Sangster, described by Burness as a highly-experienced employment tribunal advocate, is coming on board as a director.
Scottish law firm Dundas & Wilson is due to complete a merger with London-based international giant CMS Cameron McKenna on May 1, amid a raft of consolidation in the legal sector.
Unveiling the appointments to his firm's employment law team, Burness Paull chairman Philip Rodney said: "We welcome Mandy and Mel to the firm at an exciting time for Burness Paull. We continue to grow our key practice areas by investing in the very best lawyers."
Ms Laurie said: "I am very excited about joining Burness Paull, having previously spent time at the firm."
Burness Paull says it has the largest employment team in Scotland, with a client base including oil and gas services company Wood Group, investment bank Morgan Stanley, mineral water producer Highland Spring and ITN.
Sean Saluja, head of Burness's employment division, said: "Employment law continues to be under the spotlight, particularly following the (UK) Government's employment law and employment tribunal reform agenda."
Burness Paull also announced the appointment of Craig Whelton as a partner in its planning team.
He joins from Bristol-based law firm Burges Salmon.
Burness Paull said that Mr Whelton brought with him expertise in energy projects, particularly in the onshore and offshore wind, biomass and marine sectors. It added that its new recruit was an expert in development and regeneration work, and compulsory purchase law.
Mr Whelton said he was attracted to Burness by its ambitious plans to expand its planning practice.