Whenever the player equips two one-handed weapons of any type, dual wielding grants the following stats:
10% more Attack Speed while Dual Wielding
15% additional Block Chance while Dual Wielding
20% more Attack Physical Damage while Dual Wielding
The attack speed bonus is applied multiplicatively with other attack speed modifiers. These bonuses to dual wielding can be increased via passive skills. Weapons do not have to be of the same type to receive dual wielding bonuses.
There are no penalties of any kind to attacks with the player's off-hand weapon. The majority of attack skills in Path of Exile will alternate between equipped weapons for attacks,[1] swinging first with the main hand and then with the off-hand weapon. The resulting attack speed is the average of the two weapons' attack speed, so the total time for a pair of attacks is as if each weapon attacked once.
It is possible to dual-wield wands. However, players cannot wield a wand in one hand and a melee weapon in the other.