Yes, Macadamia Nut is toxic to dogs!
Dogs accidentally consuming the Macadamia Nut plants can show the following clinical symptoms: Vomiting, Prolonged Depression, Incoordination, Hypersalivaton, Sleepiness Or Excitation, Dilated Pupils, Low Body Temperature, Low Blood Pressure, Coma, Seizure And Death (In Rare Cases).
More Info About The Macadamia Nut Plant
Scientific Name: Macadamia integrifolia
Family: Proteaceae.
Also known as: Australia Nut, Queensland Nut.
The answer is based on information found on The American Society for the Prevention of Cruelty to Animals (ASPCA) website.