After the conclusion of the Western campaign, the LSSAH was expanded to brigade size. Despite this, it retained the designation regiment. A Flak battalion and a StuG Batterie were among the formations added to the LSSAH. During the later months of 1940, the regiment trained in amphibious assaults in preparation for Operation Seelöwe. After the failure of the "Battle of Britain" and the cancellation of the operation, the LSSAH was shifted to Bulgaria in preparation for Operation Marita, part of the planned invasion of Greece and the Balkans.

The Operation was launched on April 6 1941 and the LSSAH was to follow the route of the 9th Panzer Division, part of General der Panzertruppen Georg Stumme's XL.Panzer-Korps. The regiment crossed the border near Prilep and was soon deep in Greek territory. After the captured Vevi on April 10th, Sturmbannführer Kurt Meyer's (left) reinforced Aufklärungs-Abt LSSAH was tasked with clearing resistance from the Klissura Pass, south-west of Vevi and driving through to the Kastoria area to cut off retreating Greek and British Commonwealth forces. Resistance from the Greek 20th Division was fierce. According to some accounts, the SS were inspired to capture the Klissura Pass only after Meyer threw a grenade at the feet of some of his soldiers.

Strongly defended by Australian (left) , British and New Zealand troops the clearing of the Klidi pass south of Vevi ,was assigned to Sturmbannführer Fritz Witt's (right) I.Battalion. Witt's Battalion was reinforced and renamed Kampfgruppe Witt. An Australian officer wrote of the Germans' "insolence" in driving "...trucks down the main road — to within 3000 yards of our infantry", and there unloading the SS troops. The Germans were forced off the road and faced fierce resistance for more than two days. On the morning of April 12, the Germans launched a frontal assault, and by late afternoon the pass was cleared. I. Battalion LSSAH had inflicted many casualties and captured over 520 prisoners for the loss of only 37 dead and 95 wounded.

With the fall of the two passes, the main line of resistance of the Greek First Army was broken, and the campaign became a battle to prevent the escape of the enemy. On April 20, following a pitched battle in the 5,000-foot-high Metsovon Pass in the Pindus Mountains, the commander of the Greek First Army surrendered the entire Hellenic Army to Dietrich. British Commonwealth troops were now the only Allied forces remaining in Greece, and they were falling back across the Corinth Canal to the Peloponnesos. By April 26, the LSSAH had reached the Gulf of Patras, and in an effort to cut off the retreating British Commonwealth forces, Dietrich ordered that his regiment cross the Gulf and secure the town of Patras in the Peloponnesos. Since no transport vessels were available, the LSSAH commandeered fishing boats and successfully completed the crossing, despite being forced to leave much of their heavy equipment behind. By April 30, the last British Commonwealth troops had either been captured or escaped. The LSSAH occupied a position of honour in the victory parade through Athens.

Following Operation Marita, the LSSAH was ordered north, to join the forces of Army Group South massing for the launch of Operation Barbarossa. Following the LSSAH's outstanding performance during Marita, Himmler ordered that it should be upgraded to divisional status. As such, the Regiment, already the size of a reinforced brigade, was redesignated SS-Division (motorized) Leibstandarte SS Adolf Hitler. However there was no time to refit the division to full divisional status before the launch of Operation Barbarossa, the invasion of the Soviet Union, and so the new 'SS-Division' remained the size of a reinforced brigade.

The LSSAH was attached to the LIV.Armee-Korps and held in reserve during the opening stages of the attack. In August, it was transferred to III.Panzer-Korps, part of Generalfeldmarschall Ewald von Kleist's (left) Panzergruppe 1. During this time, the LSSAH was involved in the Battle of Uman and the subsequent capture of Kiev. During this time, the division was involved in heavy fighting, with Meyer's Abteilung particularly distinguishing itself. In early September, the division was transferred back to LIV.Armee-Korps, preparing to launch an offensive to clear the Crimean peninsula. The operation was launched on 17 September 1941. The LSSAH was involved in heavy fighting for the town of Perekop, before advancing across the Perekop Isthmus to assault the Soviet defensive positions near the Tarter Ditch. In November, the LSSAH was transferred back to Panzergruppe 1 and took part in the heavy fighting for the city of Rostov-on-Don, which was captured in late November. During Operation Barbarossa, the division had penetrated 960 kilometers into Soviet territory.

Heavy Soviet counterattacks during the winter meant that Army Group South had to fall back from Rostov-on-Don to defensive lines on the river Mius. The LSSAH spent the winter fighting ferocious defensive battles in temperatures of down to -40°C, with minimal winter clothing and only 150 grams of rations per man per day. Despite this, the division held. After the spring Rasputitsa had cleared, the exhausted division joined in Fall Blau, partaking in the fighting to retake Rostov-on-Don, which was recaptured in late July, 1942. Severely understrength and completely exhausted, the LSSAH was pulled out of the line. The division was ordered to the Normandy region of occupied France to join the newly formed SS-Panzer-Korps and to be reformed as a panzergrenadier division.