In general, no. But the quality of the workout is variable. Depending on your age and fitness level, it is possible to get your heart-rate up high enough for cardiovascular benefit while walking, but it isn't easy and you really have to be going for it. Personally when I was in worse shape than I am now, I could get my HR up to 120 BPM while walking briskly, which for my age group at the time, was just about the bare minimum for cardiac benefit. Now it's hard for me to walk fast enough to get it up that high. Running or jogging easily puts me over 120 BPM.
Now, of course, walking is better than being sedentary.