An LED lamp includes a lampshade, an LED module and a heat sink supporting and cooling the LED module. The heat sink includes a heat absorbing portion having a base plate for mounting the LED module thereon, and engaging with the lampshade for enclosing the LED module. A plurality of fins is formed on a top of the heat absorbing portion, and the fins extend outwardly beyond an outmost edge of the heat absorbing portion. A sidewall connects outmost ends of the fins. A plurality of apertures are defined between the outmost edge of the heat absorbing portion, the fins and the sidewall for allowing an airflow to flow from a bottom to a top of the heat sink via the apertures, thereby to effectively cool the heat sink and accordingly the LED module.