New-born lambs have limited energy reserves and need a rapid access to colostrum to maintain homeothermy and survive. The object of this study was to investigate the importance of neonatal lamb behaviour in the maintenance of its body temperature and survival. The time taken to stand and suck after birth and rectal temperatures were determined in 72 crossbred lambs (progeny of crossing 1/2 Rhamani and 1/2 Finnish). In addition, blood samples were collected at 1, 24 and 72 h after birth. The obtained sera were assayed for thyroid hormones (T3 and T4), known to be involved in heat production and phosphorous element (ph) which is essential for energy metabolism. The obtained results revealed that, low birth weight and triplet lambs were behaviourally less active at birth and had less T3, T4, Ph and body temperatures values over the first 3 days of life than lambs of heavy or medium birth weight and single or twin lambs. Thus, light weight and triplet lambs were highly susceptible to hypothermia and were exposed to high rate of mortality (18.75 and 16.66%) during the neonatal period than other lambs (3.84, 10.00, 4.55, and 9.38 %, respectively). Therefore, the present study concludes that neonatal lamb behaviour, specifically success in standing and obtaining colostrum are extremely important for thermoregulation and survival of the neonate.